Abstract
The alteration of spatial patterns of landscape interrupts water balance components in Bilate basin of Ethiopia. The aim is to characterize the spatio-temporal variation of surface-subsurface hydrological water balance using the WetSpass model comprising of soil type, topography, groundwater depth, and slope. Environment for Visualizing Images (ENVI) and Arc-GIS software were assimilated for the classification of Landsat images from 1989 to 2019 replicating the forest, shrub, and grasslands which decrease by 4.0%, 9.41%, and 14.87%, respectively, and agricultural land increasing by 27.06% from 1989 to 2019. The goodness of fit in surface runoff and subsurface flow for the two model outputs with the square of regression (R2) of 0.79 and 0.81, while the root mean square errors (RMSEs) 8.26 mm and 8.39 mm for 1989 and 2019, respectively, were calculated. Average annual interception, groundwater recharge, surface runoff, and actual-evapotranspiration were 36.4 mm, 127.34 mm, 614.95 mm, and 517.59 mm, respectively, revealing that WetSpass works remarkably in simulating the components of the hydrological water balance.
Highlights
Water is important, limited, exposed, and valuable natural resource on the planet
Ethiopia is predominantly covered with a mountainous topography, which relies on rainfall-runoff processes [2]. ough the country is known as the tower of Africa, rich in surface and groundwater resources fostered by 12 major river basins, 22 lakes, and other renewable sources [3], sporadic droughts, erosion, flooding, and drying of streams, springs, and lakes seem to be increasing [4] year after year. e hydrological cycle of the area is affected by sporadic change in infiltration, interception, runoff, and evapotranspiration (EVT) which is usually carried out by human activities changing the land surface [5]
In lieu of the topography, the basin is classified into three subbasins; upper, middle, and lower with an average of 1165 mm of rainfall, and it has been recorded that the annual rainfall varies between 1280–1339, 1061–1516, and 769–956 mm in the upper, middle, and lower part of the basin, respectively [22]. e Bilate basin stretches 225 km southwards before joining Lake Abaya and covers Southern Nations Nationalities and Peoples’ Region (SNNPR) which includes Hadiya, Kembata-Tambaro, Gurage, Silte, Wolaita, Alaba zones, Sidama regional states, and a small part of south-central Oromia regional state
Summary
Lack and scarcity of freshwater from the surface resources may enhance the use of exploiting groundwater in the coming years irrespective of the country or continent [1]. E hydrological cycle of the area is affected by sporadic change in infiltration, interception, runoff, and evapotranspiration (EVT) which is usually carried out by human activities changing the land surface [5]. Due to radical growth of population and high urbanization and dynamics of land use, surface runoff has been used imprudently [6]. Human interferences have been sensationally changing the land cover with a considerable impact on the soil, water, and atmosphere [7]. Stresses on groundwater resources have been increasing due to economic development and massive population growth [9]
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