Satellite-based assessment of upstream regulation impacts on downstream reservoir dynamics and agricultural activity between the Turkey and Syria 

Water has long been a strategic resource in the semi-arid landscapes of Mesopotamia, a region spanning Turkey, Syria, and Iraq, where the Tigris and Euphrates rivers form the lifeline of societies. As water scarcity intensifies due to a combination of climatic stressors and anthropogenic pressures, the governance of transboundary rivers has become critical for ensuring health, food security, and regional stability. The stakes are particularly high in this basin, where upstream–downstream asymmetries shape political relations and exacerbate vulnerabilities.The long-standing dispute between Turkey, the upstream hegemon, and Syria, a downstream user, has deepened in the past decade with the emergence of a de facto Kurdish administration in northern and eastern Syria along Turkey’s southern border. This political reality adds complexity to water governance, intersecting with security concerns and competing narratives of resource control. Despite the centrality of water in these dynamics, empirical verification of water availability and flow remains limited. Data scarcity, driven by sparse in-situ measurements and restricted access to hydrological information, hampers assessment of scarcity and its implications for conflict and cooperation.Against this backdrop, this study examines whether upstream reservoir dynamics at the Atatürk Dam in Turkey are reflected in storage variations at the downstream Tishrin reservoir in Syria, and whether these hydrologic changes are accompanied by detectable signals in agricultural activity. We compiled multi-year satellite-derived time series for both reservoirs and nearby agricultural zones, including reservoir surface water level, precipitation, temperature, evapotranspiration, soil moisture, and NDVI-based vegetation activity. Variables were harmonized to a common monthly scale and prepared for anomaly-based analysis to reduce seasonal confounding.A qualitative review of the time series indicates baseline hydroclimatic contrasts between the two study regions. Precipitation, soil moisture, and baseline NDVI appear lower in the Tishrin-side agricultural area than in the Atatürk-side agricultural area, suggesting a more water-limited system and greater sensitivity to variability in water availability. These background differences provide context for downstream vulnerability but do not explain the temporal structure of reservoir storage fluctuations and associated vegetation anomalies. The reservoir and vegetation time series suggest downstream dynamics are constrained within a lower-productivity envelope, consistent with stronger exposure to moisture stress and limits in irrigation reliability.To move from qualitative evidence to attribution, we test whether upstream and downstream reservoir dynamics are coupled once hydroclimatic controls are considered. We use time-series comparison and statistical controls to separate signals linked to reservoir operations from those attributable to regional climate variability, drawing on precipitation, temperature, evapotranspiration, and soil moisture as contextual drivers. We then investigate whether vegetation activity across surrounding agricultural areas covaries with local reservoir conditions and hydroclimatic stress, using NDVI anomalies as an integrated measure of crop response. Finally, land use/land cover trajectories will be evaluated to place short-term variability in a longer-term landscape context, with mapping consistency to ensure apparent shifts in cultivation are not conflated with classification artifacts. This integrated satellite-based framework offers a robust, adaptable basis for evaluating transboundary water-management influences on downstream storage and agricultural conditions in a politically complex setting.