Assessment of Hydrological Intervention for Hallur (4d4d4b) Sub Watershed of Rattihalli Taluk, Haveri District, Karnataka

Abstract

The Halluru sub-watershed in Rattihalli taluk, Haveri district, demonstrates complex hydrological and agro-ecological dynamics shaped by topography, land use, soil properties and climatic variability. DEM analysis reveals elevations ranging from 450 to 808 m. Actual evapotranspiration (AET) exhibits considerable spatial and seasonal variation, from 542 to 988 mm, with lower values in high-elevation rainfed areas and higher values in low-lying irrigated zones with deeper soils and denser vegetation. Land use was predominantly agricultural (≈50.7% cropland; 6.1% plantations), with minimal forest cover (0.2%) and moderate wasteland (3.3%), water bodies, and built-up areas (4.6%). Surface soils vary widely, with clayey soils dominating central and southern regions (infiltration ~2 mm/hr), clay loam in scattered patches (~7 mm/hr) and sandy clay/loamy soils in uplands (~10–14 mm/hr), influencing runoff. Rainfall analysis (2014–2022) showed that average annual rainfall of 826 mm, with kharif rainfall (≈60%) deficient in 2015, 2016 and 2018, rabi rainfall (≈20.29%) severely deficient in 2016 and 2017 and summer rainfall (≈19.37%) contributing to pre-monsoon soil moisture. The annual number of rainy days ranged from 12–25, with 0-9 days producing runoff (20-30 mm), and >30 mm events recorded only in 2021–2022. Satellitederived soil moisture maps indicate high heterogeneity, with Kharif values up to 0.28 m3 /m3 in valleys and Rabi values declining to 0.10–0.16 m³/m³ in uplands, highlighting seasonal moisture stress. Groundwater levels (2014– 2023) showed seasonal fluctuations with a long-term declining trend, exacerbated during 2019–2020 by low rainfall and intensive pumping.