Spatio-temporal distribution of water availability in Karnali-Mohana Basin, Western Nepal: Hydrological model development using multi-site calibration approach (Part-A)

Study region: Karnali-Mohana (KarMo) river basin, Western Nepal. Study focus: This study has developed a hydrological model using multi-site calibration approach for a large basin, the Karnali-Mohana (KarMo) in Western Nepal, which has a lot of potential for water resources development and contribute to the national prosperity. It further applies the model to characterize hydrology and water resources availability across spatio-temporal scales to enhance understanding on water availability and potential uses. The newly developed hydrological model in Soil and Water Assessment Tool (SWAT) is capable of reproducing the hydrological pattern, the average flows, and the flow duration curve at the outlet of the basin and five major sub-basins. New hydrological insights for this region: The model simulated results showed that about 34 % of average annual precipitation in the KarMo basin is lost as evapotranspiration, but with a large spatio-temporal heterogeneity. The Hills and Tarai are relatively wetter than the Mountains. The average annual flow volume at the basin outlet is estimated as 46,250 million-cubic-meters (MCM). The hydrological characterization made in this study are further used for climate change impact assessment (Part-B in the same journal), environmental flows assessment and evaluating trade-offs among various water development pathways, which are published elsewhere. This model, therefore, has potential to contribute for strategic planning and sustainable management of water resources to fuel the country's prosperity.