Evaluating water balance components in a tropical ecological zone under land use changes

• Published in: Ecohydrology & Hydrobiology 2024-10
• Main Authors: Nsiah, J.J., Awotwi, A., Gyamfi, C., Anornu, G.K., Boakye, E., Darko, S., Ackom, E.K.
• Format: Article
• Language: English
• Subjects: base flow; basins; Closed forest; crop yield; cropland; dry season; Evapotranspiration; forests; humans; hydrobiology; land use; land use and land cover maps; Open forest; runoff; Settlement; Soil and Water Assessment Tool model; Surface runoff; water yield; watersheds; wet season
• ISSN: 1642-3593
• DOI: 10.1016/j.ecohyd.2024.09.007

Water availability for domestic, institutional, and agricultural production is threatened by the continuous change in land use land cover (LULC). These changes in LULC features affect the dynamics of the hydrological processes such as surface runoff, infiltration, and evapotranspiration, resulting in variations in water availability especially, for human consumption and crop yield. Therefore, the Soil and Water Assessment Tool (SWAT) hydrological model was deployed to simulate the Pra River Basin (PRB)’s water balance response to changing LULC from 1986 to 2020. Open and closed forests reduced from an area of 11,071 km2 to 5902 km2 and 5125 km2 to 4990 km2 while settlement and cropland increased from 1100 km2 to 2392 km2 and 5303 km2 to 9320 km2 representing an average annual expansion rate of +24.7 km2/yr and +118 km2/yr respectively over the three decades. The growth in settlement and cropland resulted in an upsurge of more than 33 % and 20 % in surface runoff and water yield respectively, but decreases of over 4 % and 17 % in evapotranspiration and baseflow respectively. These changes have resulted in a seasonal increase in surface runoff, baseflow, and evapotranspiration (ET) during the wet season but a decrease during the dry season. The PRB has experienced a dramatic decline in forest areas, chiefly in areas where settlement and farmlands have been expanded. The areas where surface runoff and water yield showed significant upsurge and reduction in ET are the northwestern and southern enclaves of the basin. These findings can aid in effectively planning and managing land use to control the gradually depleting water resources in the basin.