Abstract:
Insufficient understanding of the available water resources and inadequate coordination in their
management frequently lead to competition among users for these limited water resources. This
study assessed surface water potential and water demand in the Dijo watershed to optimize
benefits while maintaining ecological requirements. To achieve this goal the SWAT model was
used to analyze surface water potential, following sensitivity analysis, calibration, and validation
using SWAT_CUP. Additionally, the Water Evaluation and Planning (WEAP) model was utilized
to determine water demands. Various scenarios were developed to analyze future water demand,
supply requirements, and unmet demand from 2025 to 2050. The determination of water demand
for crop water requirements and irrigation water requirements was conducted using the
CROPWAT 8.0 model. The results showed that the available surface water potential in the
watershed was 411.31 MCM in 2024. calibration and validation results showed satisfactory
performance, with R² = 0.73, NSE = 0.68, and PBIS = -4.7 for calibration, and R² = 0.79, NSE =
0.62, and PBIS = -9.1 for validation. The analysis conducted during the study period of 2024
revealed that the water demands were 20.54 MCM for domestic consumption, 2.054 MCM for
industrial activities, 35.06 MCM for irrigation, 12.54 MCM for livestock, and 41.13 MCM for
environmental flow requirements. The total water demand for the year 2024 was recorded at
111.33 MCM, accounting for 27% of the surface water potential available and there was no annual
unmet demand; however, shortages occurred in November, December, and January due to low
flow conditions. The study recommends harvesting rainfall during the rainy season to mitigate
shortages in November, December, and January. The reference scenario was projected in two time
horizons, the total water demand will increase to 125.8 MCM in 2035 and 156.92 MCM in 2050.
For a high population growth scenario, the total water demand will increase to 133.11 MCM in
2035 and 187.85 MCM in 2050. For the irrigation farm expansion scenario, the total water
demand will increase to 134.34 MCM in 2035 and 180.54 MCM in 2050. For the combination
scenario(both High population growth rate and Irrigation farm expansion), the total water
demand will increase to 141.62 MCM in 2035 and 211.43 MCM in 2050.
Keywords: Dijo watershed, SWAT, WEAP, CROPWAT, SWAT_CUP water demand, and
