Iran Water–Climate Atlas

Section I: Introduction

(Atlas Dossier: Iran Water–Climate Atlas)

Iran’s geographic identity is shaped by its mountains, basins, and plateaus, creating a landscape where water is unevenly distributed and often scarce. The country depends fundamentally on the hydrological functions of the Alborz and Zagros ranges, which capture atmospheric moisture, generate snowfall, and feed rivers and aquifers that sustain urban, agricultural, and industrial systems across much drier interior regions. This mountain-dependent arrangement has historically supported settlement patterns across the Central Plateau and the southern and eastern lowlands despite limited rainfall.

Over the past decades, long-term climatic and environmental trends have begun to alter this balance. Rising temperatures, declining snowpack, increased evapotranspiration, and land degradation reduce the reliability of water supply across large parts of the country. Groundwater reserves—once considered a stable buffer—are now experiencing rapid depletion and structural collapse. Subsidence in several major basins indicates that aquifers are losing not only water but also their ability to recover.

These physical changes interact with demographic, economic, and infrastructural dynamics. Iran’s population has grown steadily, with the majority concentrated in cities that rely on groundwater pumping and interbasin transfers. Industrial sectors, particularly in metallurgy, petrochemicals, and agriculture, depend on stable water and energy availability. As hydrological conditions shift, these systems encounter increasing stress, leading to potential interruptions in service, reduced economic output, and migration pressures.

This dossier provides a structured overview of the physical systems that underlie Iran’s water security, the mechanisms driving their degradation, and the spatial patterns of vulnerability across the country. It integrates hydrology, climatology, soil science, and demographic analysis to outline the conditions shaping future habitability. While not a forecasting document, it identifies scenario horizons—2030, 2040, and 2050—in which different regions face varying degrees of stress based on observable trends.

The purpose of this section, and of the dossier as a whole, is to supply a scientifically grounded reference for understanding Iran’s evolving environmental landscape. By linking climatic drivers, hydrological processes, and geographic constraints, the dossier establishes a factual baseline that supports subsequent analysis, mapping, policymaking, and scenario development across the Atlas, RavenIntel, and editorial domains.

Section II: Physical Geography of Iran

Iran’s physical geography is defined by a series of sharply contrasting landforms that together create a complex hydrological and climatic system. The dominant features are the Alborz and Zagros mountain ranges, which function as the primary engines of precipitation and water distribution. These highlands surround and enclose extensive interior basins, including the Central Plateau and the deserts of Dasht-e Kavir and Dasht-e Lut. The arrangement of mountains, plateaus, and basins governs where water forms, where it is stored, and where it becomes scarce.

Show the entire hydrological spine of Iran:
Mountains → Rivers → Basins → Aquifers → Cities.

[Atmosphere]  
   ↓ moist air  
[Mountain Range: Alborz/Zagros]
   Snowpack → Meltwater  
   ↓  
[Rivers/Basins]  
   Surface flow → infiltration  
   ↓  
[Unsaturated Zone]  
   Soil moisture, percolation  
   ↓  
[Groundwater/Aquifer]  
   Storage → recharge  
   ↓  
[Cities & Agriculture]  
   extraction → return flow → evaporation

Key message

Iran is a mountain-fed civilization.
The plateau is hydrologically dead without mountain snowpack.

2.1 Mountain Systems: Alborz and Zagros

Alborz Range

Stretching along the southern coast of the Caspian Sea, the Alborz range intercepts moist air masses and produces significant orographic precipitation, much of it as winter snowfall. This snowpack represents one of Iran’s most critical natural reservoirs. Meltwater feeds rivers flowing toward Tehran, Qazvin, Mazandaran, and Golestan, supporting both urban centers and agricultural zones. The narrow coastal strip north of the range benefits from high rainfall, making it one of the few naturally humid regions in the country.

Zagros Range

The Zagros extend from northwest Iran to the Persian Gulf, forming a broad physiographic zone of folded mountains and intermontane valleys. The range captures moisture from westerly airflows, generating snow in higher elevations and rainfall in foothills. The Zagros supply water to numerous major basins in western and southwestern Iran, supporting rivers such as the Karun, Karkheh, and Dez. The valleys within the range host some of the most stable long-term climatic conditions in the country.

2.2 Plateau and Inland Basins

The Central Plateau occupies a vast internal depression bordered by the Alborz, Zagros, and Kopet Dag mountains. Elevation varies widely, but most of the plateau is arid or semi-arid. Rainfall is low, evaporation is high, and surface water is limited. Historically, the plateau supported major settlements through a combination of qanat systems, seasonal rivers, and groundwater extraction.

Within the plateau lie two major desert systems:

• Dasht-e Kavir, a salt desert with extensive playas and crusted soils
• Dasht-e Lut, one of the hottest recorded landscapes on Earth

These deserts expand through broad alluvial fans, dry riverbeds, and sedimentary plains, creating natural barriers and limiting agricultural potential.

2.3 River Basins

Iran’s river basins are predominantly fed by mountain precipitation and snowmelt. Key basins include:

• Karun Basin – The largest by flow volume, originating in the Zagros and supplying Khuzestan’s agriculture and industry.
• Karkheh Basin – Fed by Zagros snowmelt; supports extensive agricultural zones but highly sensitive to temperature and precipitation shifts.
• Dez Basin – A critical component of southwestern Iran’s water system; storage and irrigation networks are central to regional food production.
• Zayandeh Rud Basin – Originates in the Zagros and flows toward the Esfahan region, historically sustaining one of Iran’s major population and industrial centers. Flow variability has increased significantly.
• Helmand Basin – Shared with Afghanistan; supplies Sistan’s terminal wetlands (Hamun system). Highly vulnerable to upstream reductions and climatic drying.
• Caspian Tributaries – Short, steep rivers flowing northward from the Alborz, supporting humid coastal regions.

Each basin displays different sensitivities to temperature rise, snowpack decline, and land-use change.

2.4 Aquifer Systems

Iran’s aquifers form the hidden backbone of national water storage. Many developed urban centers—Tehran, Esfahan, Qom, Mashhad, Kerman, Yazd—depend heavily on groundwater extraction.

Key characteristics:
• Alluvial aquifers beneath major basins provide large but finite storage.
• Recharge is controlled by infiltration from rivers and mountain runoff.
• Over-extraction has led to declining water tables and subsidence.
• Fossil aquifers exist in some arid zones but lack meaningful recharge.

Aquifer depletion limits the resilience of cities and agricultural systems, especially where surface water is insufficient to offset pumping.

Section III: Climate and Hydrological Structure

Iran’s climate is governed by its position between arid subtropical zones and mountainous regions that intercept limited atmospheric moisture. Because most of the country lies in rain-shadowed interior basins, the hydrological system depends heavily on the interaction between mountain precipitation, surface runoff, and groundwater recharge. Climate change modifies each part of this sequence, altering the timing, volume, and distribution of available water.

3.1 Orographic Precipitation and Atmospheric Dynamics

Moist air masses from the west, northwest, and south encounter Iran’s mountain chains, where forced uplift cools the air and produces condensation. This process creates the majority of Iran’s precipitation, particularly in winter. Snowfall is concentrated in high elevations of the Alborz and Zagros ranges, forming seasonal reservoirs that release water gradually through spring and early summer.

Key characteristics:
• The Caspian coastal plain receives some of the highest rainfall due to moisture trapped by the Alborz.
• The western slopes of the Zagros receive moderate to high precipitation.
• The interior plateau remains shielded from these systems and is largely arid.

Climate warming alters this dynamic by increasing the elevation at which snow forms and by shortening the duration of snowpack, reducing the buffering effect of delayed melt.

3.2 Seasonal Patterns and Temperature Trends

Iran experiences a predominantly dry summer and a precipitation-driven winter cycle. Average annual precipitation varies from more than 1,500 mm in the Caspian region to less than 100 mm in parts of the Lut and Kavir deserts.

Temperature trends show:
• Increased winter temperatures, reducing snowfall fractions.
• Earlier spring melt, shifting river discharge toward shorter, more intense periods.
• Higher summer temperatures that amplify evaporation and stress water systems.
• More frequent heat extremes in southern and eastern regions.

These shifts decrease the predictability of water availability and intensify pressure on surface reservoirs.

3.3 Evapotranspiration and Atmospheric Losses

Under rising temperatures, the rate of evapotranspiration increases across all ecosystems. Even when precipitation levels remain stable, higher heat results in a greater proportion of water returning directly to the atmosphere. The Penman–Monteith equation, widely used to estimate reference evapotranspiration, indicates that temperature, solar radiation, and wind speed collectively raise atmospheric demand.

Implications include:
• Reduced effective rainfall reaching soil and aquifers.
• Greater irrigation requirements in agricultural zones.
• Higher water losses from reservoirs and channels.
• Increased stress on urban cooling and power generation systems.

Evapotranspiration now accounts for a dominant share of Iran’s hydrological losses, overshadowing surface runoff and deep percolation in many basins.

Incoming:
   Rainfall ↓
   Snowmelt ↓
   River inflow ↓

Outgoing:
   Evaporation ↑↑↑
   Soil evaporation ↑↑
   Transpiration ↑
   Atmospheric heat uplift ↑↑↑ (wet-bulb)

3.4 Soil Moisture Dynamics and Infiltration Constraints

The movement of water from surface to subsurface depends on soil texture, structure, salinity, and vegetation cover. In many Iranian basins, repeated drought cycles, intensive land use, and thermal stress have degraded soil surfaces. Crusted and hydrophobic soils resist infiltration, causing rainfall to produce runoff rather than recharge.

Consequences include:
• Reduced groundwater replenishment, even in wet years.
• Increased flash flooding due to rapid runoff.
• Declining soil moisture storage, which exacerbates drought intensity.
• Greater erosion and sediment transport into reservoirs.

The loss of infiltration capacity represents a structural bottleneck in the hydrological system, limiting future resilience.

3.5 Surface Water and River Flow Variability

Iran’s rivers depend primarily on snowmelt. As snowpack declines and melt occurs earlier, river hydrographs shift away from stable seasonal flows toward shorter, less predictable pulses. This affects dam operations, irrigation scheduling, and interbasin transfer schemes.

Observed trends include:
• Declining perennial flow in many rivers, especially Zayandeh Rud and tributaries of the Karun and Karkheh.
• Increased seasonal variability, with multiple basins showing extended dry-season minima.
• Reduced long-term reservoir reliability due to lower inflows and higher evaporation.

Surface water systems now display higher volatility and reduced buffering capacity.

3.6 Groundwater Recharge and Storage Behavior

Groundwater remains a critical water source across Iran, particularly in urban basins. Recharge derives from infiltration along riverbeds, mountain fronts, and irrigated fields. As infiltration rates decline, natural recharge decreases, leading to sustained groundwater depletion. Pumping often exceeds recharge by wide margins, and in several basins, fossil groundwater is being extracted with no meaningful replenishment.

Key patterns:
• Falling water tables in major urban basins such as Tehran, Esfahan, Kerman, Shiraz, and Mashhad.
• Deepening extraction thresholds that increase energy costs and reduce water quality.
• Signs of compaction in aquifer systems, indicating permanent loss of storage capacity.

Groundwater decline reduces the strategic flexibility of water managers and increases vulnerability to climatic shocks.

Section IV: Soil and Land-System Dynamics

Iran’s land systems are undergoing rapid transformation driven by climatic warming, declining vegetation cover, groundwater depletion, and long-term land-use pressure. Soil quality, infiltration behavior, and structural stability determine whether rainfall or diverted water can enter groundwater systems, sustain agriculture, or support ecological resilience. As these characteristics deteriorate, the capacity of landscapes to absorb and retain water decreases, amplifying hydrological and climatic stress.

4.1 Soil Moisture and Infiltration Processes

Under natural conditions, Iran’s mountain foothills, alluvial fans, and river terraces possess soils capable of moderate infiltration. These soils historically supported the recharge of shallow aquifers and fed qanat systems that transferred groundwater to settlements and farmlands.

Several factors now limit this process:

• Surface crusting following intense heat and evaporation cycles.
• Salinization, especially in irrigated zones where evaporation concentrates salts at the surface.
• Reduced organic matter due to vegetation loss and declining agricultural resilience.
• Compaction from machinery, overgrazing, and repetitive land disturbance.

As infiltration capacity declines, rainfall increasingly becomes surface runoff, reducing groundwater recharge even in above-average precipitation years. Soil surfaces exposed to prolonged drought often become hydrophobic, causing rainfall to repel rather than penetrate the ground.

4.2 Hydrophobicity and Runoff Dominance

Hydrophobic soil conditions arise when organic compounds or mineral salts accumulate on soil surfaces during prolonged drying phases. When re-wetted, these layers resist moisture penetration.

In many Iranian basins, hydrophobicity has increased due to:

• Rising temperatures that intensify soil drying cycles.
• Shrinking vegetative cover, reducing shading and organic replenishment.
• Recurrent droughts that create alternating wet–dry cycles.
• Wildfire activity in some foothill zones, altering soil chemistry.

The result is a shift from infiltration-driven hydrology to runoff-dominated hydrology. Flash floods have become more frequent in regions where surface conditions prevent soil absorption. This behavior accelerates erosion, damages agricultural land, and deposits sediment into reservoirs and riverbeds, reducing storage and channel stability.

4.3 Desertification Fronts and Land Degradation

Iran’s desertification fronts represent areas where vegetation cover, soil structure, and water availability decline simultaneously, often irreversibly. These fronts advance along transitional zones between semi-arid plains and hyper-arid deserts.

Key desertification zones include:

• Edges of the Dasht-e Kavir, affecting Semnan, Garmsar, Ardestan, and Na’in corridors.
• Northern and western margins of the Dasht-e Lut, influencing Kerman, Bam, and Rigan regions.
• Southern plateau margins near Yazd and Ardakan, where declining groundwater pushes agricultural retreat.
• Sistan region, where terminal-basin drying and upstream reductions in the Helmand River supply exacerbate land degradation.

Desertification reduces the land’s capacity to support agriculture, undermines rural livelihoods, and increases vulnerability to dust storms and soil erosion.

4.4 Soil Structure, Aquifer Support, and Ground Stability

The structural integrity of soils determines how water can move through unsaturated and saturated zones. Where groundwater extraction exceeds recharge, pore spaces collapse, producing land subsidence. This is pronounced in several Iranian cities and basins.

Processes include:

• Lowering of groundwater tables, reducing pore pressure.
• Effective stress increase, causing soil grains to compact.
• Structural collapse of aquifer layers, eliminating storage volume.
• Surface subsidence, damaging buildings, pipelines, and road networks.

Subsidence rates in parts of the Tehran Basin, Esfahan Plain, and Rafsanjan–Kerman region rank among the highest documented globally. Once these structures collapse, they cannot be restored, limiting future groundwater storage even if precipitation improves.

4.5 Salinization and Soil Productivity Decline

Irrigation systems in arid climates face inherent salinization risks. As water evaporates from fields, dissolved salts accumulate in the root zone. Without sufficient flushing flows or drainage systems, salinity increases to levels incompatible with crop growth.

Current trends show:

• Rising soil salinity in Khuzestan, Kerman, Yazd, and parts of Esfahan.
• Reduction in agricultural yields and crop diversity.
• Soil hardening and loss of fertility.
• Increased reliance on groundwater with higher salinity levels.

Salinization reduces agricultural resilience and contributes to migration pressures from rural areas into already-stressed urban environments.

4.6 Erosion, Sediment Transport, and Reservoir Impacts

Declining vegetation cover and increased runoff have accelerated erosion in many catchments. Sediment loads travel downstream, affecting reservoirs and irrigation systems.

Impacts include:

• Reduced reservoir capacity over time.
• Increased turbidity, affecting treatment requirements.
• Altered flow patterns in rivers and channels.
• Reduced lifespan of hydraulic infrastructure.

These changes reduce the effectiveness of water storage systems that are essential for seasonal and interannual variability management.

Section V: Collapse of Hydrological Subsystems

Iran’s water system is composed of interdependent subsystems—snowpack, rivers, aquifers, soils, and reservoirs—that historically maintained balance through delayed meltwater release, seasonal flow patterns, and groundwater buffering. As climatic conditions shift and extraction intensifies, these subsystems weaken concurrently. Their decline reduces overall resilience and reshapes water availability across basins.

5.1 Snowpack Decline and Meltwater Variability

Snowpack in the Alborz and Zagros mountains serves as Iran’s natural long-term water storage. It moderates seasonal variability by releasing water gradually through spring and early summer. Rising winter temperatures reduce snow accumulation and increase the proportion of precipitation falling as rain. Earlier melt timing shifts river discharge toward shorter, more concentrated periods.

Key effects:

• Reduced late-summer flow in snow-fed rivers.
• Lower annual runoff volume in many basins.
• Increased frequency of mid-winter floods due to rain-on-snow.
• Greater interannual variability, complicating storage and planning.

Loss of snowpack weakens the entire downstream hydrological architecture.

5.2 River Flow Reduction and Basin Failure

Most Iranian rivers rely heavily on snowmelt rather than rainfall. As snowpack declines, flows diminish in volume and consistency. Several basins show multi-decade negative trends, with more severe reductions during warm years.

Basin-specific trends:

• Karun: declining discharge, higher salinity intrusion risk in the downstream delta.
• Karkheh: reduced inflow to agricultural zones; dam reliability decreasing.
• Dez: variable flow with increasing low-water periods; pressures on irrigation systems.
• Zayandeh Rud: intermittent surface flow, extended dry phases through Esfahan.
• Helmand: terminal basin drying and high dependency on upstream releases.

Basin failure is not uniform; each river’s response reflects local climatic, hydrological, and land-use dynamics. However, the common pattern is reduced perennial flow, higher volatility, and diminished predictability.

5.3 Loss of Perennial Surface Water

Perennial streams and springs historically supported rural settlements and agricultural valleys. Many have shifted to seasonal or episodic flow patterns. Springs that previously provided stable baseflow now appear only after intense rainfall events. In areas dependent on qanats, reduced recharge leads to lower flow or complete system failure.

Consequences:

• Abandonment of marginal agricultural land.
• Increased rural-to-urban migration.
• Loss of ecological services in riparian zones.
• Pressure on remaining water sources and competition for access.

Surface water systems can decline rapidly once river flow becomes intermittent.

5.4 Reservoir Constraints and Evaporation Losses

Reservoirs in Iran were designed around past hydrological patterns. With reduced inflow and higher temperatures, storage efficiency has declined. Evaporation from large surface reservoirs increases during prolonged heat periods, reducing effective storage capacity.

Trends observed:

• Lower average reservoir levels due to upstream snowpack decline.
• Higher annual evaporation loss, especially in lowland basins.
• Sediment accumulation, reducing storage volume.
• Operational challenges, including difficulty meeting irrigation demands.

As reservoirs lose reliability, downstream users increasingly depend on groundwater.

5.5 Groundwater Depletion and Long-Term Impacts

Groundwater extraction has exceeded recharge in many basins for decades. The resulting drawdown reduces groundwater availability and increases water extraction costs. Moreover, falling water tables allow saline water from deeper geological layers to rise, degrading water quality.

Implications include:

• Reduced pumping access as water tables decline.
• Rising salinity in wells used for urban and agricultural supply.
• Reduced aquifer resilience to drought cycles.
• Permanent loss of storage in compacted aquifers.

As groundwater levels drop, the buffering role that sustained cities through drought periods diminishes.

5.6 Aquifer Structural Collapse and Subsidence

Where groundwater extraction creates persistent deficits, aquifer matrices collapse. This has occurred in basins beneath Tehran, Esfahan, Kerman, Yazd, and other cities. Satellite data and field measurements show some regions experiencing subsidence rates among the highest documented globally.

Key structural impacts:

• Irreversible compacted layers, reducing storage capacity.
• Surface sinking, damaging infrastructure and altering drainage patterns.
• Increased flood vulnerability, especially in subsided urban zones.
• Reduced potential for artificial recharge, as pore spaces no longer exist.

Subsidence signals a fundamental transition: once collapsed, affected aquifers can no longer serve as reliable strategic reserves.

5.7 Integrated Subsystem Decline

The simultaneous weakening of snowpack, surface flow, infiltration capacity, groundwater levels, and storage structures results in a systemic decline:

• Less water enters the system.
• More water is lost to evaporation.
• Less water infiltrates into soils.
• Aquifers store less water and collapse under stress.
• Rivers lose both volume and consistency.
• Reservoirs lose efficiency and evaporate more water.

The system’s redundancy erodes, reducing flexibility during periods of drought or heat extremes.

Section VI: Urban System Stress

Iran’s cities depend on a tightly coupled water–energy–infrastructure nexus that becomes increasingly fragile as hydrological conditions degrade. Urban systems require stable supplies of drinking water, cooling capacity, electricity, wastewater treatment, and industrial process water. When water availability becomes unstable, multiple urban subsystems falter simultaneously. This section describes how climatic warming, hydrological decline, and land-system degradation converge to place Iranian cities under escalating stress.

6.1 Water Dependency in Urban Basins

Most major Iranian cities are located in basins historically fed by rivers, alluvial aquifers, and qanat systems. Over time, groundwater extraction expanded to meet rising urban and industrial demands. As surface water inputs decline, reliance on groundwater increases further.

Characteristics of current urban water dependency:

• High extraction volumes relative to recharge in Tehran, Esfahan, Shiraz, Kerman, Qom, and Mashhad.
• Decreasing groundwater quality, especially where salinity rises with falling water tables.
• Aging distribution systems that lose significant volumes to leakage.
• Dependence on interbasin transfers, increasing vulnerability to upstream climatic or policy changes.

These dependencies create conditions where disruptions propagate quickly through urban systems.

6.2 Cooling Demand and Energy System Overload

Rising temperatures increase the cooling demand in cities. Air conditioning systems draw substantial electricity, which in turn requires water for power plant cooling. As heat events intensify, energy demand peaks coincide with reduced water availability and decreased generation efficiency.

Urban consequences include:

• Peak-load stress on electrical grids during warm periods.
• Reduced efficiency of thermal power plants under high ambient temperatures.
• Increased risk of rolling blackouts, especially during heat waves.
• Higher water consumption for power plant cooling, adding pressure to scarce supplies.

This feedback loop—heat driving cooling demand, which requires more water—tightens urban fragility during extreme weather.

6.3 Water–Energy–Cooling Failure Cascade

Cities can experience cascading failure when water supply or electricity systems become unstable. Interdependence between water treatment, pumping stations, cooling systems, and electrical distribution creates several potential pathways for disruption.

Typical cascade sequence:

1. Heat wave increases cooling demand.
2. Electricity demand exceeds capacity, reducing grid stability.
3. Water pumping and treatment systems become strained or slow down.
4. Cooling systems in buildings and hospitals become less effective.
5. Industrial operations slow, raising economic losses.
6. Urban services degrade, leading to public health risks.

In some cities, even short interruptions in water treatment or distribution can generate significant operational strain.

6.4 Urban Infrastructure and Subsidence Risks

Subsidence associated with groundwater extraction presents serious risks to urban infrastructure. In major basins, subsidence cracks and ground-level shifts have affected highways, pipelines, buildings, and drainage networks.

Infrastructure at risk:

• Water and sewage pipelines, which can fracture under differential ground movement.
• Roads and foundations, especially in northern Tehran, western Esfahan, and Kerman Plain.
• Stormwater systems, which can become misaligned, reducing capacity.
• Electrical substations and transmission corridors, vulnerable to shifting ground levels.

Structural damages increase maintenance burdens and complicate future urban expansion.

6.5 Industrial, Agricultural, and Service Sector Pressures

Urban economies rely on industries that consume large volumes of water, including steel, petrochemicals, cement, textiles, and food processing. As water availability declines, these sectors face production constraints.

Key pressures:

• Reduced industrial output due to water shortages and cooling disruptions.
• Increasing operational costs as deeper wells and energy for pumping become required.
• Agriculture retreating from peri-urban zones, reducing food supply resilience.
• Service sector vulnerability to power and cooling disruptions during heat waves.

Economic pressure often triggers migration toward regions with more stable conditions, placing additional strain on receiving areas.

6.6 Urban Habitability and Public Health Considerations

Heat, pollution, water scarcity, and infrastructure vulnerabilities combine to influence urban habitability. During extreme heat events, reduced cooling capacity can pose health risks, especially for vulnerable populations. Water quality issues associated with declining aquifers or intermittent supply can affect sanitation and disease transmission.

Urban habitability risks include:

• Heat stress morbidity, amplified by insufficient cooling.
• Reduced air quality during dust events linked to land degradation.
• Higher incidence of waterborne diseases where treatment becomes inconsistent.
• Impact on emergency services, which depend on stable power and water supply.

As these stresses mount, cities become less resilient to shocks.

6.7 Variation in Urban Vulnerability Across Regions

Urban vulnerability differs across Iran:

• Tehran faces severe subsidence, water table decline, and grid strain.
• Esfahan depends on diminishing surface flows and industrial cooling capacity.
• Shiraz and Mashhad face rising demand relative to supply.
• Kerman–Bam zones are exposed to extreme heat and groundwater depletion.
• Ahvaz endures some of the highest heat stress levels and salinity issues.

The most resilient urban zones tend to be located in or near the Zagros highlands or the Caspian region, where climatic and hydrological conditions remain comparatively favorable.

Section VII: Uninhabitability Index

The Uninhabitability Index provides a structured method to compare the relative long-term habitability of different regions in Iran by integrating climatic, hydrological, soil, infrastructural, and demographic stress indicators. It is a composite analytical framework, not a prediction. Its purpose is to identify where physical constraints converge most strongly and to highlight zones where environmental and infrastructural pressures may exceed the thresholds required to sustain stable human settlement.

The index is designed for atlas-level reference and supports cross-domain work in RavenIntel, Broad Horizon, and planning analysis.

7.1 Purpose and Scope

The index organizes Iran’s environmental stress landscape into a single, interpretable map. It captures the combined impacts of:

• Climatic pressure
• Water system degradation
• Soil and land-system decline
• Urban fragility
• Population density
• Exposure to extreme heat

It does not evaluate governance or political dynamics directly, except where these influence water and infrastructure systems. The index offers a spatial baseline for scenario horizons in later sections.

7.2 Structure of the Composite Index

The index aggregates five dimensions. Each dimension consists of measurable or semi-quantifiable indicators.

1. Climate Stress

• Maximum summer temperature trends
• Frequency of extreme heat days
• Wet-bulb temperature thresholds
• Heatwave persistence

2. Water Resource Stress

• Snowpack decline intensity
• Basin flow variability
• Long-term runoff anomalies
• Reservoir reliability

3. Soil and Land-System Stress

• Infiltration reduction
• Hydrophobicity prevalence
• Desertification front proximity
• Salinization extent
• Erosion and sediment movement

4. Groundwater and Subsurface Stress

• Rate of aquifer depletion
• Subsidence intensity
• Falling water table trends
• Loss of storage capacity

5. Urban and Demographic Stress

• Cooling-energy-water dependency
• Infrastructure vulnerability
• Population density in at-risk zones
• Exposure to flood or subsidence hazards

Each dimension is normalized to enable comparison across regions. Combined, they generate an overall stress score.

7.3 Class Definitions

Based on combined scores, regions fall into three broad categories.

1. Severe Uninhabitability (High Stress)

Defined by:

• Persistent extreme heat (including wet-bulb thresholds approaching or exceeding 30–35°C)
• Very low surface water availability
• Irreversible aquifer compaction
• Strong desertification signals
• Limited infrastructure resilience

Typical regions:

• Southern Khuzestan
• Sistan terminal basin
• Southern Kerman and Bam/Rigan belt
• Desert-fringe zones of Lut and Kavir

These areas face acute long-term constraints.

2. High-Risk Zones (Moderate to High Stress)

Defined by:

• Declining aquifer reliability
• Intermittent surface flow
• High cooling-energy-water interdependence
• Population pressure
• Soil degradation

Typical regions:

• Tehran Basin
• Esfahan Plain
• Shiraz Basin
• Yazd–Ardakan corridor
• Qom–Kashan belt

These zones remain functional but face sustained stress under warming scenarios.

3. Moderate Future Risk (Low to Moderate Stress)

Defined by:

• Relatively stable precipitation
• Higher elevation or cooler climate
• Remaining aquifer resilience
• Less exposure to extreme summer temperatures

Typical regions:

• Zagros highlands (northwest to southwest arc)
• Caspian coastal zone
• Northern Kermanshah and Kurdistan
• Tabriz–Urmia highland belt

These regions form the backbone of long-term habitability and potential safe relocation corridors.

7.4 Regional Interpretation

Mapping the index reveals the spatial pattern of environmental stress:

• High-risk zones cluster around the central plateau, major inland cities, and southern lowlands.
• Relatively resilient zones cluster around the Zagros chain, northwest highlands, and the Caspian littoral.
• Stress intensifies along transition zones—desert fringes, subsiding basins, and downstream heat zones—which often become demographic pressure points.

The index helps identify where infrastructure adaptation, resource management, and long-term spatial planning are most critical.

Section VIII: Survival Horizons (2030–2040–2050)

The survival horizons framework organizes Iran’s evolving environmental and infrastructural pressures into three indicative time bands: 2030, 2040, and 2050. These are not fixed predictions but scenario markers that reflect when cumulative climatic, hydrological, and land-system stresses are likely to produce qualitatively different conditions in various regions. Each horizon is defined by the interaction of the Uninhabitability Index with observable trends in water availability, heat stress, infrastructure resilience, and demographic concentration.

8.1 Methodology and Assumptions

The horizons are constructed using:

• Long-term climate warming trajectories and heatwave frequency.
• Documented trends in snowpack, river flow, and reservoir performance.
• Groundwater depletion and subsidence rates.
• Soil degradation and desertification progression.
• Urban dependence on water–energy–cooling systems.
• Population density and exposure in at-risk basins.

The framework assumes a continuation of current trajectories without major structural changes in water governance, large-scale technological breakthroughs, or abrupt shifts in climate policy. It is designed to be refined as new data emerge.

8.2 2030 – Critical Zone Horizon

By around 2030, several regions are expected to experience sustained high stress, marked by:

• More frequent and severe heatwaves, including elevated wet-bulb temperatures.
• Reduced reliability of river flows in key basins.
• Significant groundwater level declines in already-depleted aquifers.
• Expansion of desertification fronts into marginal agricultural zones.

Likely characteristics:

• Khuzestan lowlands: combination of extreme heat, salinity, and industrial water demands.
• Sistan: terminal basin stress with high dependence on upstream inflows and local groundwater.
• Southern Kerman–Bam–Rigan corridor: aggravated heat, groundwater exhaustion, and land degradation.
• Desert-fringe settlements along the Kavir and Lut edges.

In these areas, daily life remains possible but increasingly challenging. Water interruptions, heat stress events, and localized migration from rural to urban centers become recurrent features. The 2030 horizon marks the threshold at which environmental pressures become a persistent structural factor in regional planning and livelihoods.

8.3 2040 – Structural Decline Horizon

Around 2040, stresses deepen in regions that are currently functioning but structurally vulnerable:

• Aquifers in several major basins approach critical depletion.
• Subsidence intensifies, affecting urban infrastructure more broadly.
• Surface water variability increases, complicating reliable reservoir management.
• Heat and humidity combinations further constrain outdoor labor and agricultural productivity.

Likely affected regions:

• Tehran Basin: intensified subsidence, higher extraction costs, grid and cooling stress.
• Esfahan Plain: intermittent or unreliable Zayandeh Rud flows, compounded by groundwater decline.
• Shiraz Basin: heightened temperature stress and reduced hydrological buffer.
• Yazd–Ardakan–Na’in corridor: greater dependence on deep groundwater and increased uninhabitability signals.
• Qom–Kashan region: cumulative aquifer stress and desertification proximity.

Under this horizon, the combination of physical limits and infrastructural strain leads to structural decline in some urban and peri-urban areas. Agricultural and industrial activities become harder to sustain at previous levels. Population movements from these basins toward more stable highland and northern regions likely increase in magnitude.

8.4 2050 – Terminal Zone Horizon

By around 2050, parts of the Central Plateau and several desert-fringe basins are projected to face conditions that approach or cross long-term habitability thresholds. This does not imply total abandonment but indicates that sustaining large populations under conventional infrastructure and economic models may become increasingly difficult.

Key elements:

• Irreversibly compacted aquifers that can no longer function as strategic water storage.
• Extreme summer heat and wet-bulb temperatures that constrain outdoor activity and increase health risks.
• Minimal surface water availability, with many flows intermittent or absent.
• Advanced desertification and soil degradation, leaving little productive land.

Likely terminal-stress zones:

• Interior parts of the Central Plateau with limited recharge and high heat exposure.
• Segments of the Semnan–Garmsar–Na’in belt near the Kavir.
• Deep interior zones adjacent to the Lut Desert.
• Stressed pockets in southern Kerman and other marginal basins.

In these areas, long-term sustainability of dense settlement becomes questionable without continuous high-cost interventions or a fundamental reconfiguration of economic and infrastructural models.

8.5 Interactions Between Horizons and Migration

The horizons are sequential but overlapping. Regions that cross the 2030 threshold may continue deteriorating into the 2040 and 2050 categories if no mitigating measures are taken. As this occurs, population movements are likely:

• From 2030-critical to relatively safer highland and northern regions.
• From 2040-structural-decline basins as systemic reliability falls.
• Away from 2050-terminal zones where constraints become structural and persistent.

The horizons thus provide a temporal-spatial framework for analyzing when and where migration pressures are likely to intensify.

8.6 Planning and Policy Relevance

The survival horizons can be used to:

• Prioritize adaptation investments (e.g., infrastructure reinforcement, cooling resilience, water conservation).
• Guide long-term spatial planning, including potential relocation corridors and new urban development.
• Inform risk communication and emergency preparedness strategies.
• Support regional and international dialogue on shared water and climate challenges.

Because the horizons represent scenario bands rather than fixed dates, they can be adjusted as new climate projections and observational data become available.

Section IX: Migration Dynamics

As climatic and hydrological stresses intensify, Iran’s population distribution is likely to change. Migration dynamics provide the human response layer to environmental constraints. While economic, social, and political factors will shape outcomes, physical limits on water, heat, and land productivity establish a structural backdrop. This section outlines a three-stage conceptual model of internal migration under worsening environmental conditions.Section IX: Migration Dynamics

9.1 Drivers and Framework

Migration in this context arises from overlapping drivers:

• Environmental: water scarcity, heat extremes, land degradation.
• Economic: declining agricultural yields, industrial disruptions, job losses.
• Social: reduced quality of life, service degradation, health risks.
• Infrastructural: repeated service interruptions (water, electricity, transport).

The model follows a progression from local, short-distance movement to larger-scale, inter-regional relocation.

9.2 Stage 1 – Rural to Urban Movement

The first stage, already observable in many regions, involves the movement of rural households from increasingly marginal agricultural zones into nearby towns and cities.

Key triggers:

• Declining groundwater levels in rural wells.
• Increased frequency of crop failure due to drought and heat stress.
• Expansion of desertification into formerly productive fields.
• Salinization reducing soil fertility.

Typical flows:

• From peripheral villages in Khuzestan, Kerman, Yazd, and Sistan into regional urban centers.
• From desert-fringe settlements toward provincial capitals and secondary cities.

Consequences:

• Expansion of informal settlements around cities.
• Increased demand for urban services, housing, and employment.
• Greater stress on already fragile urban water and energy systems.

9.3 Stage 2 – Urban to Regional Movement

As urban systems themselves face recurrent stress—through water shortages, cooling failures, or economic decline—movement extends beyond local basins toward more climatically and hydrologically stable regions.

Triggers at this stage:

• Repeated or prolonged water-supply interruptions.
• Chronic power outages during heat waves.
• Loss of industrial jobs dependent on reliable water and energy.
• Visible infrastructure damage linked to subsidence or flooding.

Emerging patterns:

• Migration from Esfahan, Shiraz, Qom, Kerman, and parts of Tehran toward higher-elevation or northern cities.
• Movement from southern lowlands to foothill or highland towns within the Zagros.
• Increased interest in relocation to the Caspian region and northwestern highlands.

Stage 2 represents a shift from basin-scale to inter-basin population redistribution.

9.4 Stage 3 – National Retreat to Safe Belts

In a more advanced stress scenario, large portions of the Central Plateau and some lowland regions may no longer support dense populations under prevailing infrastructure and economic models. At this stage, migration becomes a broad, multi-regional redistribution.

Destination regions:

• Caspian Safe Water Zone—higher rainfall, lower heat stress.
• Zagros Highland Belt—relatively cooler conditions, more stable local water systems.
• Northwest highlands—Tabriz, Urmia, and surrounding areas with remaining resilience.

Characteristics:

• Multi-year, cumulative movement of households rather than a single event.
• Reconfiguration of economic centers and labor markets.
• Increased pressure on land, infrastructure, and ecosystems in receiving regions.

Stage 3 migration reshapes the national demographic map.

9.5 Bottlenecks and Corridors

Physical geography constrains where people can move.

Likely bottlenecks:

• Alborz passes linking Tehran Basin to the Caspian coastal plain.
• Zagros passes connecting plateau cities to highland valleys.
• Transit corridors between Kerman, Yazd, and central/northern basins.

Corridors of movement:

• From the Central Plateau toward the Zagros and Caspian belts.
• From southern lowlands into highland foothills.
• From Sistan into either internal urban centers or, in some cases, across borders.

These corridors will experience heightened demand for housing, services, and transport capacity.

9.6 Demographic Scale and Absorptive Capacity

Under central-scenario assumptions, internal movements over several decades could involve tens of millions of people. The ability of receiving regions to absorb this population without replicating existing vulnerabilities depends on:

• Land-use planning and zoning.
• Investment in water-efficient infrastructure.
• Distributed urban development (avoiding single megacity concentration).
• Protection of local ecosystems to maintain hydrological stability.

Without such measures, pressure on safe belts could generate new stress cycles.

9.7 Interaction with External Migration

While this dossier focuses on internal dynamics, environmental pressures may also influence cross-border movement. Outmigration could occur where internal absorption and adaptation capacity are insufficient or unevenly distributed. This introduces regional implications for neighboring countries and international policy, though the magnitude and direction of such flows depend heavily on non-environmental factors.

Section X: Safe Zones and the Future Cities Corridor

The long-term habitability of Iran will depend on regions where climatic, hydrological, and geological conditions remain comparatively stable under warming trends. These areas—primarily located along the Caspian littoral and the Zagros highlands—offer the most sustainable combination of rainfall, moderate summer temperatures, groundwater resilience, and lower subsidence risk. Together, they form the conceptual backbone of a Future Cities Corridor, a polycentric network of settlement nodes aligned with Iran’s most viable environments.

10.1 Caspian Safe Water Zone

The Caspian coastal plain and adjacent foothills represent one of the most hydrologically favorable regions in Iran. This zone benefits from:

• High annual precipitation relative to the rest of the country.
• Dense forest cover and relatively stable soils.
• Short river catchments with reliable flow.
• Lower exposure to extreme heat and wet-bulb thresholds.

Key characteristics:

• Sustained renewable freshwater supply, driven by moisture from the Caspian Sea.
• Agricultural and ecological resilience, due to stable moisture regimes.
• Reduced dependence on deep groundwater, compared to plateau cities.

Limitations include limited land availability due to the narrow coastal plain, high population density in some areas, and environmental sensitivity. Nonetheless, this region is one of the strongest candidates for long-term settlement stability.

10.2 Zagros Highland Belt

The Zagros highlands form a chain of valleys and plateaus stretching from the northwest to the southwest. Elevation moderates temperatures, and precipitation patterns—though variable—remain more favorable than in interior basins.

Advantages:

• Moderate summer heat, especially in higher-elevation valleys.
• Distributed water sources, including local springs and mountain-fed streams.
• Greater long-term groundwater resilience, with some aquifers still functioning.
• Lower subsidence risk, due to geological composition and lower extraction intensity.

The region includes several major urban centers (e.g., Kermanshah, Sanandaj) and numerous secondary cities that could serve as anchors for expanded settlement networks.

10.3 Tier-1, Tier-2, and Tier-3 Settlement Nodes

The Future Cities Corridor is not a single megacity project but a distributed network of hubs and supporting towns.

Tier 1 – Primary Urban Anchors

Large existing cities in resilient zones:

• Rasht / Bandar-e Anzali (future Capital possibility)
• Sari
• Gorgan
• Tabriz (northwestern anchor)
• Sanandaj
• Kermanshah

These cities possess existing infrastructure and regional economic roles.

Tier 2 – Expansion Nodes

Secondary towns or highland urban centers with capacity for managed growth:

• Ardabil
• Maragheh
• Borujerd
• Shahrekord
• Mahabad
• Khorramabad

These nodes offer space, elevation advantages, and proximity to more stable hydrological pockets.

Tier 3 – Planned New Towns

New settlements or redesigned expansions aligned with corridor logic:

• Highland valley developments in proximity to water-secure basins.
• Satellite communities near Tier-1 cities to reduce urban saturation.
• Corridor-linked settlements located along ecological and hydrological thresholds.

Tier-3 nodes serve to distribute population evenly and avoid repeating patterns of over-concentration seen in Tehran or Esfahan.

10.4 Environmental and Infrastructural Logic of the Corridor

The corridor is guided by physical realities rather than political boundaries or administrative divisions. Its logic includes:

• Hydrological stability: prioritizing zones with reliable water sources.
• Thermal moderation: elevational cooling lowers summer stress.
• Ground stability: limiting settlement growth in subsidence-prone basins.
• Polycentric design: avoiding dependence on a single infrastructural hub.
• Ecological integration: maintaining forests, wetlands, and soil structures that support local hydrology.

This approach aligns settlement planning with environmental capacity.

10.5 Risks and Constraints in Safe Zones

Even resilient zones have limits.

Challenges include:

• Land scarcity in the Caspian plain, due to topography and existing development.
• Ecological sensitivity, particularly forest ecosystems and wetlands.
• Increased demand on local water and infrastructure systems under large-scale migration.
• Potential localized heat increases from urban expansion.
• Inter-regional inequalities, as resources shift toward northern and western belts.

Thus, while safe zones provide a foundation for future habitability, they require careful planning and governance to avoid new vulnerabilities.

10.6 Long-Term Spatial Rebalancing

The corridor concept provides a framework for reorienting Iran’s population distribution. In a high-stress scenario, relocation may occur from:

• Central Plateau → Zagros highlands
• Southern lowlands → Zagros foothills
• Tehran Basin → Alborz passes → Caspian littoral
• Kerman–Bam → Yazd → northern basins or western highlands

The outcome is a national geography in which the demographic and economic center of gravity gradually shifts northward and westward, reflecting underlying environmental constraints.

Section XI: Demographic Reallocation

Demographic reallocation describes the long-term reshaping of Iran’s population distribution under the influence of climatic, hydrological, economic, and infrastructural pressures. This process does not refer to abrupt or immediate displacement but to a multi-decade restructuring of where people can sustainably live and work. As water availability declines and heat stress intensifies in several basins, internal migration flows will likely reorient population density toward the more resilient northern and western regions. The magnitude and direction of this reallocation depend on environmental thresholds, economic conditions, and policy decisions.

11.1 National Population Context

Iran’s population is concentrated in major basins and urban centers, many of which face long-term vulnerability:

• Tehran Metropolitan Area
• Esfahan Plain
• Shiraz Basin
• Mashhad Basin
• Kerman–Bam corridor
• Yazd–Ardakan region
• Khuzestan lowlands

These areas have high dependency on groundwater and interbasin transfers, increasing exposure to climate-driven disruption.

By contrast, relatively lower population densities exist in more resilient regions:

• Caspian littoral
• Zagros highlands
• Northwestern plateau and valleys

This uneven distribution shapes the pressure points and receiving zones of demographic reallocation.

11.2 Drivers of Internal Movement

Long-term demographic shifts arise from cumulative pressures rather than isolated events. Key drivers include:

• Water insecurity: decreasing reliability of surface and groundwater sources.
• Heat exposure: recurring heatwaves and elevated wet-bulb temperatures.
• Economic contraction: declining agricultural and industrial viability in stressed basins.
• Urban fragility: infrastructure strain, cooling interruptions, subsidence impacts.
• Land degradation: declining rural productivity and soil salinization.

These factors gradually reduce the attractiveness or feasibility of residence in certain regions while increasing the relative advantages of others.

11.3 Projected Movement from High-Stress Regions

Based on the survival horizons and uninhabitability index, several areas are likely to experience sustained outmigration:

Central Plateau and Desert-Fringe Basins

• Yazd–Ardakan corridor
• Semnan–Garmsar fringe
• Na’in–Ardestan belt

Drivers include groundwater depletion, heat stress, soil degradation, and limited ecological resilience.

Southern Heat Belt

• Ahvaz, Abadan, Mahshahr
• Lower Karun and Persian Gulf coastal lowlands

Extreme heat and salinity pressures make these zones particularly vulnerable.

Sistan Basin

Dependent on external inflows and facing terminal basin dynamics, this region is sensitive to upstream variability and climatic drying.

Kerman–Bam Region

High temperatures, groundwater scarcity, and land degradation contribute to long-term demographic pressure.

11.4 Movement Toward Resilient Zones

Receiving zones are primarily located in:

Caspian Safe Water Zone

Advantages include rainfall, moderate summer conditions, and reliable surface water.
Constraints: limited land availability and ecological sensitivity.

Zagros Highland Belt

Advantages include elevation, moderate climatic conditions, and distributed water sources.
Constraints: topographical fragmentation, infrastructure capacity.

Northwestern Highlands

Including Tabriz and Urmia, these areas retain hydrological and climatic resilience relative to interior basins.

Over time, these regions may experience population increases requiring expanded planning for housing, infrastructure, and ecological conservation.

11.5 Urban Rebalancing and Future Settlement Patterns

Demographic reallocation shifts the national urban hierarchy:

• Traditional megacenters (e.g., Tehran, Esfahan) may face relative contraction or slower growth.
• Highland and northern regional cities may expand in economic and demographic importance.
• New towns and satellite settlements may emerge in proximity to resilient basins.

The Future Cities Corridor framework supports this transition by providing a structured approach to distributing population across multiple hubs.

11.6 Implications for Labor Markets and Economic Geography

Population shifts influence the location of economic activity:

• Water-intensive industries may need to relocate toward areas with more stable supply.
• Agriculture may consolidate in higher-rainfall or groundwater-secure zones.
• Services and knowledge sectors may reorganize around expanding highland cities.
• Logistics and transport networks may align with new demographic centers.

Over time, Iran’s economic geography may realign around the corridor zones.

11.7 Limitations and Variables Affecting Reallocation

The magnitude of demographic movement depends on several factors:

• Governance and planning capacity to support adaptation.
• Economic diversification, enabling relocation of industries and services.
• Infrastructure investments in receiving regions.
• Natural variability and uncertainty in climatic projections.
• Social preferences and cultural attachments to place of origin.

While environmental factors set broad constraints, human decisions determine how migration unfolds.

Section XII: Governance and Regional Implications

Governance determines how effectively Iran can respond to escalating climate and water pressures. While physical constraints shape long-term habitability, policy choices, institutional arrangements, and cross-border dynamics influence how societies experience and manage these pressures. Water scarcity intersects with land management, urban planning, energy supply, agriculture, and international relations. This section outlines the key governance dimensions affecting Iran’s ability to navigate environmental change.

12.1 National Water Governance Structure

Iran’s water governance system involves multiple institutions at national, provincial, and basin levels. Responsibilities include regulation, allocation, infrastructure development, and monitoring. Historically, the system has relied on:

• River regulation through dam construction.
• Groundwater extraction for urban and agricultural demand.
• Interbasin transfers to supplement stressed basins.
• Irrigation networks designed for past climatic conditions.

As environmental stress increases, these traditional approaches face diminishing returns. Long-standing practices, such as groundwater overdraft, become increasingly unsustainable under warming conditions.

Challenges include:

• Over-allocation of surface water rights relative to actual flows.
• Limited enforcement capacity for groundwater extraction regulations.
• Fragmented basin-level governance and competing stakeholder interests.
• Infrastructure designed for historical, not future, hydrological variability.

Improving governance requires aligning institutional frameworks with climatic realities.

12.2 Infrastructure Planning and Adaptation Capacity

Infrastructure resilience will determine whether cities and regions can adapt to climatic pressures.

Key areas of governance influence:

• Water supply diversification (surface, groundwater, reuse, efficiency).
• Reservoir management under more variable inflows.
• Urban cooling and energy grid stability during heat extremes.
• Subsidence mitigation measures, including extraction control.
• Agricultural adaptation, including cropping system adjustments and irrigation efficiency improvements.

Effective planning must incorporate long-term climate projections, not solely historical records.

12.3 Agricultural Policy and Land Management

Agriculture remains a major water user, particularly in arid basins where irrigation sustains crop production. Governance challenges include:

• Incentive structures that encourage high water use.
• Limited monitoring of well extraction and irrigation efficiency.
• Soil salinity management in regions with high evaporation.
• Vulnerability of rural communities to hydrological decline.

Policy adaptation may require transitioning to lower water-use crops, adjusting irrigation methods, and supporting alternative livelihoods in regions facing long-term agricultural contraction.

12.4 Urban Governance Challenges

Urban areas face intersecting pressures:

• Maintaining water quality and quantity under supply stress.
• Expanding cooling infrastructure for heat adaptation.
• Managing land subsidence and its impact on critical systems.
• Coordinating interbasin transfers to meet peak demand.
• Planning for population inflows from rural and vulnerable regions.

Urban governance must address both short-term service reliability and long-term habitability.

12.5 Cross-Border Water Issues

Iran shares several key basins with neighboring countries, making international cooperation essential.

Significant shared systems include:

• Helmand Basin with Afghanistan.
• Aras and Lesser Kura systems with Azerbaijan and Armenia.
• Tigris-related tributaries influencing western Iran.

Challenges:

• Upstream development, including dam construction, alters inflows.
• Climate change reduces shared water availability.
• Coordination frameworks may be limited or under strain.
• Terminal basins (e.g., Hamun) are particularly sensitive to upstream decisions.

Sustaining ecological systems in border regions requires durable agreements and integrated basin management.

12.6 Environmental Governance and Ecosystem Preservation

Healthy ecosystems contribute to hydrological resilience by stabilizing soils, supporting infiltration, moderating temperatures, and sustaining biodiversity. Governance priorities include:

• Forest conservation in the Caspian and Zagros regions.
• Wetland restoration (e.g., Hamun, Urmia, Shadegan).
• Managing desertification through land-use planning and reforestation.
• Controlling overgrazing and erosion in foothill zones.

Integrating ecosystem services into policy frameworks strengthens long-term climate adaptation.

12.7 Regional and International Implications

Iran’s environmental trajectory carries implications beyond its borders:

• Migration pressures may affect neighboring countries.
• Shared water systems require cross-border cooperation.
• Energy supply (including cooling and hydropower) connects to regional grids.
• Economic shifts in agriculture, industry, and services may influence trade patterns.

International collaboration on climate adaptation, technology transfer, and basin management can improve resilience.

12.8 Governance Under Uncertainty

Future environmental conditions involve significant uncertainty due to:

• Variability in climate projections.
• Economic and demographic change.
• Technological developments in water management and energy systems.
• Political and institutional evolution.

Effective governance must embrace scenario planning and adaptive management, with flexible strategies that can adjust as new data and conditions evolve.

Section XIII: Scientific Basis and Theoretical Foundations

The analysis presented in this dossier is grounded in established scientific principles from hydrology, climatology, soil science, environmental physics, and migration studies. This section outlines the foundational theories and empirical frameworks used to interpret Iran’s environmental trajectory. These concepts provide the analytical backbone for understanding how climatic and hydrological systems interact with landforms, urban infrastructure, and demographic patterns.

The section is written in a neutral, reference-oriented manner suitable for an atlas dossier. Citations align with well-recognized scientific literature.

13.1 Hydrology and Water Balance Theory

Budyko Framework

A conceptual model describing how precipitation is partitioned between evapotranspiration and runoff as a function of available energy and moisture.
Relevance: explains why Iran loses a large fraction of water to the atmosphere under high temperatures—even in years with stable rainfall.

Catchment Water Balance Equation

Defines the relationship between precipitation, evapotranspiration, runoff, and storage change.
Relevance: provides the conceptual basis for assessing changes in river basin performance.

Interception and Orographic Precipitation Dynamics

Mountains influence rainfall distribution through forced air uplift and condensation.
Relevance: explains the role of the Alborz and Zagros as Iran’s primary water-generating systems.

13.2 Snowpack, Meltwater, and Seasonal Hydrology

Energy-Balance Models of Snowmelt

Temperature-driven melt processes follow predictable patterns under warming conditions.
Relevance: connects rising winter temperatures to earlier melt, reduced snowpack storage, and altered river seasonality.

Snow-Rain Transition Thresholds

Studies show that a small rise in winter temperature can convert snowfall into rainfall in marginal elevations.
Relevance: supports observed reductions in Iran’s snow-fed river flow reliability.

13.3 Soil Science and Infiltration Theory

Horton Infiltration Model

Describes how infiltration capacity declines over time during rainfall events.
Relevance: used to conceptualize infiltration reduction on crusted or degraded soils across Iranian basins.

Green–Ampt Equation

A physically based infiltration model incorporating soil suction and hydraulic conductivity.
Relevance: foundational for understanding infiltration constraints in arid soils.

Richards Equation

Governs movement of water in the unsaturated zone.
Relevance: essential for conceptualizing recharge limitations in compacted or desiccated soils.

Soil Hydrophobicity Mechanisms

Explains how organic compounds and drying cycles create water-repellent surfaces.
Relevance: characterizes runoff dominance in degraded Iranian soils.

13.4 Aquifer Mechanics and Subsidence Theory

Darcy’s Law (Groundwater Flow)

Describes the movement of water through porous media.
Relevance: fundamental to understanding aquifer depletion and flow behavior under extraction.

Terzaghi’s Effective Stress Principle

Explains how reductions in pore pressure cause soil grains to compact.
Relevance: primary mechanism behind irreversible aquifer collapse and land subsidence.

Compaction and Consolidation Models

Identify thresholds beyond which aquifers lose storage capacity permanently.
Relevance: supports analysis of subsidence in Tehran, Esfahan, and Kerman basins.

13.5 Evapotranspiration and Atmospheric Physics

Penman–Monteith Equation

Standard method for estimating evapotranspiration based on radiation, temperature, humidity, and wind.
Relevance: explains why evaporation increases sharply with heat in Iran’s climate.

Wet-Bulb Temperature and Human Heat Stress

Defines thresholds beyond which human thermoregulation becomes ineffective.
Relevance: used to assess habitability constraints in southern and eastern Iran.

Radiative Forcing and Regional Warming

Climate models show enhanced warming over arid land surfaces.
Relevance: underpins long-term temperature rise in Iran’s plateau and lowland regions.

13.6 Desertification and Land Degradation Theory

UNEP Desertification Framework

Identifies factors such as vegetation loss, soil erosion, salinity, and overgrazing as drivers of land degradation.
Relevance: aligns with observed expansion of degraded zones around the Kavir and Lut deserts.

Salinization Dynamics in Irrigated Agriculture

Explains accumulation of salts due to evaporation exceeding leaching.
Relevance: critical for understanding agricultural decline in Khuzestan, Kerman, and Yazd.

Erosion and Sediment Transport Models

Describe how soil loss accelerates under low vegetative cover and intense runoff.
Relevance: supports observations of reservoir sedimentation and landscape instability.

13.7 Urban System and Infrastructure Theory

Water–Energy Nexus

Electricity generation requires water for cooling; cooling systems require electricity; and both depend on stable water supply.
Relevance: explains cascading failures during heatwaves.

Infrastructure Fragility and Threshold Behavior

Urban systems fail non-linearly once critical thresholds are crossed.
Relevance: underpins the four-week urban failure model described in earlier sections.

Subsidence Impacts on Infrastructure Integrity

Ground-level changes alter the function of pipelines, roads, and drains.
Relevance: central to vulnerability analysis in subsiding cities.

13.8 Migration Studies and Demographic Theory

Environmental Migration Framework (Black et al.)

Identifies five drivers of migration: environmental, economic, social, political, demographic.
Relevance: supports the staged migration model used in Section IX.

Slow-Onset Hazard Displacement

Describes migration triggered by gradual environmental decline rather than sudden events.
Relevance: applicable to groundwater depletion, heat stress, and desertification in Iran.

Carrying Capacity and Urbanization Models

Explain how cities absorb population until system constraints force redistribution.
Relevance: underlies long-term shifts toward the Zagros and Caspian belts.

13.9 Integration Across Disciplines

The complex interactions in Iran’s climate–water–land–urban system require integrated analysis:

• Hydrology determines the distribution of water.
• Climate determines thermal and evaporative stress.
• Soil science determines infiltration and land productivity.
• Aquifer mechanics determine long-term storage capacity.
• Urban planning determines vulnerability thresholds.
• Migration theory determines demographic response.

This multidisciplinary approach enables a more comprehensive understanding of Iran’s long-term habitability.

Section XIV: Limitations and Uncertainties

This dossier provides a structured, science-based assessment of Iran’s long-term environmental and habitability outlook. While grounded in well-established theories, current observational data, and robust physical models, several sources of uncertainty must be acknowledged. These uncertainties influence the timing, magnitude, and spatial detail of projected changes but do not alter the fundamental direction of the trends described.

This section clarifies the limits of current knowledge, identifies variables that may change system dynamics, and highlights areas where further data or monitoring would strengthen future assessments.

14.1 Climate Projection Uncertainty

Climate models reliably indicate warming across Iran, but there is uncertainty in:

• The rate of temperature increase, influenced by global emissions trajectories.
• The frequency and duration of extreme heat events, especially wet-bulb thresholds.
• Changes in precipitation patterns, which may vary between models.
• Snowpack sensitivity to warming, especially near elevation thresholds.

These uncertainties affect projections for snow-fed rivers, agricultural viability, and the timing of specific habitability thresholds.

14.2 Hydrological System Uncertainty

Hydrological responses depend on multiple interacting factors:

• Variability in winter precipitation and temperature affects snowpack and river flow.
• Reservoir performance depends on future inflow patterns and sedimentation rates.
• Groundwater recharge rates are poorly documented in some basins.
• Long-term impacts of climate-driven atmospheric changes on regional circulation remain uncertain.

While the direction of decline is clear, the exact pace of hydrological deterioration varies by basin.

14.3 Soil and Land-System Uncertainty

Soil behavior under prolonged drought and heat stress is complex:

• Hydrophobicity development varies with soil composition.
• Salinization rates depend on irrigation practices, evaporation intensity, and drainage conditions.
• Desertification front expansion is influenced by both climate and land-use management.
• erosion and sediment transport models rely on detailed topographic and vegetation data not uniformly available.

Local conditions may delay or accelerate degradation relative to generalized projections.

14.4 Aquifer Response and Subsidence Uncertainty

Aquifer systems involve geological heterogeneity that introduces uncertainty:

• Subsurface lithology varies widely across basins.
• Consolidation behavior depends on grain structure and clay content.
• Pumping intensity may change due to policy shifts or economic conditions.
• Subsidence does not always progress linearly; it can accelerate after thresholds are crossed.

Thus, while the overall risk of aquifer collapse is well supported, basin-level variation remains significant.

14.5 Urban System Uncertainty

Urban stress projections—particularly cascading failures—depend on:

• Future infrastructure investment levels.
• Grid modernization and cooling technology adoption.
• Water-loss reduction in distribution systems.
• Governance capacity and emergency preparedness.
• The interaction of economic cycles with migration pressures.

Urban fragility could be mitigated or worsened depending on policy and investment decisions.

14.6 Demographic and Migration Uncertainty

Migration patterns reflect both environmental and socioeconomic drivers:

• Cultural ties may delay relocation from stressed regions.
• Economic opportunities in receiving zones may be uneven or unpredictable.
• Long-term governance responses could redistribute incentives or constraints.
• National and regional policies may shape migration flows dramatically.

While spatial trends are strongly implied by environmental constraints, the magnitude and timing of population movement remain uncertain.

14.7 Governance and Policy Uncertainty

Policy responses are inherently unpredictable:

• Water-use reform may reduce extraction pressures.
• International basin agreements may stabilize inflows (e.g., Helmand).
• Diversification of energy supply may reduce vulnerability of thermal plants.
• Agricultural restructuring could reduce water demand significantly.
• Emergence of new technologies (e.g., high-efficiency desalination, cooling systems) may alter system dynamics.

Governance choices can meaningfully alter the trajectory of stress, either delaying or accelerating system thresholds.

14.8 Data Gaps and Monitoring Limitations

Several areas require improved observation:

• Basin-scale groundwater monitoring remains uneven.
• Subsidence data (InSAR) is incomplete in some regions.
• Snowpack monitoring relies on limited high-altitude instrumentation.
• Soil salinity data is not uniformly updated.
• River discharge series have gaps due to measurement limitations.

Strengthening monitoring systems would sharpen projections and improve adaptive planning.

14.9 Structural Certainties Despite Uncertainty

Despite these uncertainties, certain structural dynamics remain robust:

• Rising temperatures increase evaporation and heat stress regardless of scenario variance.
• Snowpack decline reduces the reliability of snow-fed rivers.
• Over-extraction of groundwater leads to long-term aquifer depletion and subsidence.
• Extreme heat and hydrological instability strain urban infrastructure.
• Coastal and highland regions remain comparatively more resilient than interior basins.
• The Central Plateau faces long-term habitability challenges without major interventions.

Thus, while exact timelines and magnitudes vary, the direction and nature of the long-term risks remain consistent.