| Abstract: | The present study aimed to quantify the future sustainability of a water supply system using
dynamically-downscaled regional climate models (RCMs), produced in the South Asia Coordinated
Regional Downscaling Experiment (CORDEX) framework. The case study is the Boukan dam,
located on the Zarrine River (ZR) of Urmia’s drying lake basin, Iran. Different CORDEX- models were
evaluated for model performance in predicting the temperatures and precipitation in the ZR basin
(ZRB). The climate output of the most suitable climate model under the RCP45 and RCP85 scenarios
was then bias-corrected for three 19-year-long future periods (2030, 2050, and 2080), and employed
as input to the Soil and Water Assessment Tool (SWAT) river basin hydrologic model to simulate
future Boukan reservoir inflows. Subsequently, the reservoir operation/water demands in the ZRB
were modeled using the MODSIM water management tool for two water demand scenarios, i.e.,
WDcurrent and WDrecom, which represent the current and the more sustainable water demand scenarios,
respectively. The reliability of the dam’s water supply for different water uses in the study area was
then investigated by computing the supply/demand ratio (SDR). The results showed that, although
the SDRs for the WDrecom were generally higher than that of the WDcurrent, the SDRs were all <1,
i.e., future water deficits still prevailed. Finally, the performance of the water supply system was
evaluated by means of risk, reliability, resiliency, vulnerability, and maximum deficit indices, and the
combination of the indices to estimate the Sustainability Group Index (SGI). The findings indicated
that, compared to the historical period for both the water demand scenarios, WDcurrent and WDrecom,
the average SGI of each RCP would be decreased significantly, particularly, for the more extreme
RCP85 scenario. However, as expected, the SGI decrease for the WDrecom was less than that of the
WDcurrent, indicating the advantage of implementing this more sustainable water demand scenario. |