EFFECTS OF LAND COVER ON GROUNDWATER DYNAMICS IN MIDDLE YALA CATCHMENT, KENYA

Abstract

Groundwater depletion is on an increasing trend. Soil moisture content plays a major role in plant growth, nutrient transport, and oxygen balance. Assessment of soil water balance is crucial for understanding water dynamics to optimize water and fertilizer use. The main objective of the study was to examine the effects of land cover on groundwater in the middle Yala catchment, Kenya.. The specific objectives of this study were to investigate the groundwater recharge rate, to evaluate soil water distribution in the vadose zones for various land uses and to simulate the effects of various land cover on the flow in the vadose zone. Rainfall, Evapotranspiration, and root water uptake will be the main components of water balance. Therefore, intensive field experiments and HYDRUS-1D numerical modelling were applied to investigate the effects of land cover on groundwater dynamics. Primary data in this study were collected under varying environmental conditions: tree canopy and grassland plantations. Secondary data were collected from the weather station in Vihiga County. The HYDRUS 1D model was used to simulate the relationship between the two simulated scenarios under varying soil texture. Rainfall and soil data were combined with temperature and humidity collected by TMS sensors as model variables to determine the trends in water fluctuations. The findings revealed grassland sites maintained an average volumetric moisture content (VMC) of 32–35%, while eucalyptus sites dropped to as low as 18–20% during peak dry periods. The impact of seasonal rainfall patterns varied on the soil moisture, and the rate of simulated recharge in grassland was 4.2 mm/day on average as opposed to 1.6 mm/day on average in the area with eucalyptus cover. The model was able to well describe the trends in soil moisture in grassland but the interactions with eucalyptus were a problem. Finally choosing vegetation covers that boost recharge of groundwater and recommends controlled growth of eucalyptus is significant to sustainable farming. Future research suggestions are the long-term monitoring, investigation of various vegetation effects, and the combination of climate change and remote sensing technology. These observations are important in enhancing management strategies of groundwater and how land cover practices contribute to sustainability of groundwater in the area.