Identifying Major Hydrologic Change Drivers in a Transboundary Highly
Managed Endorheic Basin: Integrating Hydro-ecological Models and Time
Series Data Mining Techniques
Saline endorheic lakes play a crucial role in ecological regulation and
biodiversity conservation in semi-arid regions. They provide a wide
range of ecosystem services such as habitat for aquatic life and
migratory birds, water supply, mineral extraction, and recreation.
Although saline lakes are critical to ecological health and human
wellbeing, they are being shrunk at alarming rates in recent decades,
representing some of the most threatened ecosystems in the world.
Factors contributing to lake degradation are directly linked to the
expansion and intensification of agriculture in the 20th century and its
intertwined effect with global warming. However, quantifying the
relative contribution of climate variability and anthropogenic stressors
in water budget dynamics of the lakes is challenging. Hydrologic
processes of highly managed agricultural landscapes are complex and the
lack of spatial data in endorheic basins with transboundary water issues
further contribute to this problem. In this study, we developed a
modeling framework that integrates the Soil and Water Assessment Tool
(SWAT) simulations with seasonal trend decomposition by LOESS (STL),
residual analysis for anomaly detection, and time series clustering, to
identify the major drivers of lake trend and seasonal shrinking
patterns. This modeling framework was applied to the Salton Sea Basin
(SSB), host of the largest inland lake in California. Salton Sea’s water
level has declined by 32% over the last 25 years, causing a massive
bird and fish die-off, and a regional asthma crisis due to the spreading
of toxic dust from the exposed playa. Results suggest that decreases in
Colorado River allocation are causing the lake to shrink, not changes in
the irrigation efficiency or the climate regime as commonly believed.
Our results are expected to assist decision-makers with a robust
modeling tool to evaluate the environmental tradeoffs in formulating and
implementing timely adaptation and mitigation strategies across the SSB
while minimizing their economic consequences.