Assessing basin blue-green available water components under different
management and climate scenarios using SWAT
Abstract
Because the pattern of climate and water demand varies, available water
(AW) must be determined to facilitate policymaking and to prepare for
sustainable use of water resources. This study investigated the
components of basin water availability using a comprehensive water
balance framework based on SWAT model. The resulting system is capable
of supporting systematic presentation of the current status and past
trends in the components of AW, presentation of interlinkages of blue
and green water components, assessment of measures on AW at farm and
basin scales, spatial and temporal variations of AW components under
different water policies and climate scenarios and evaluation of water
shortage. To explore this methodology, the system was applied to the
Tashk-Bakhtegan basin (Iran). The results for the historical period
showed wide ranges for the blue water components, which was 113 mm on
average. While it was 48.2 mm for green water components. Similarly,
blue water was more sensitive than green water to the future annual
precipitation variations. Evaluation of the construction of the Durodzan
dam (the basin’s major water storage facility) showed that it has
drastic impact on the spatial blue AW components. Such that they are
increased in the adjacent subbasin up to 97% and reduced to half the
status quo in the downstream subbasins. The basin has also experienced
30% increase in its cropped areas between 1987 and 2015 that has
resulted 1500 MCM water shortage in the current condition. Considering
the framework as a relatively easy-to-use tools with readily available
data, is strongly recommended for other regions.