The effects of land use and land cover (LULC) on groundwater recharge and surface runoff and how these are affected by LULC changes are of interest for sustainable water resources management. However, there is limited quantitative evidence on how changes to LULC in semi-arid tropical and subtropical regions affect the subsurface components of the hydrologic cycle, particularly groundwater recharge. Effective water resource management in these regions requires conclusive evidence and understanding of the effects of LULC changes on groundwater recharge and surface runoff. We reviewed a total of 27 studies (2 modeling and 25 experimental), which reported on pre-and post land use change groundwater recharge or surface runoff magnitude, and thus allowed to quantify the response of groundwater recharge rates and runoff to LULC. Comparisons between initial and subsequent LULC indicate that forests have lower groundwater recharge rates and runoff than the other investigated land uses in semi-arid tropical/ subtropical regions. Restoration of bare land induces a decrease in groundwater recharge from 42% of precipitation to between 6 and 12% depending on the final LULC. If forests are cleared for rangelands, groundwater recharge increases by 7.8 ± 12.6%, while conversion to cropland or grassland results in increases of 3.4 ± 2.5 and 4.4 ± 3.3%, respectively. Rehabilitation of bare land to cropland results in surface runoff reductions of between 5.2 and 7.3%. The conversion of forest vegetation to managed LULC shows an increase in surface runoff from 1 to 14.1% depending on the final LULC. Surface runoff was reduced from 2.5 to 1.1% when grassland is converted to forest vegetation. While there is general consistency in the results from the selected case studies, we conclude that there are few experimental studies that have been conducted in tropical and subtropical semi-arid regions, despite that many people rely heavily on groundwater for their livelihoods. Therefore, there is an urgent need to increase the body of quantitative evidence given the pressure of growing human population and climate change on water resources in the region.

Land use change, especially conversion of native forests can have large impacts on water resources. Large scale conversion of native forests to agricultural land has occurred in the last few decades in the Mau Forest region. To quantify and understand landscape hydrologic responses, this study aimed at evaluating the effects of land use on soil infiltration, saturated hydraulic conductivity, bulk density, sorptivity, and soil moisture retention. A total of 136 plots representing five different land uses (native forest: n = 39, forest plantations: n = 14, tea plantations: n = 24, croplands: n = 23 and pasture: n = 36) were sampled in three catchments with similar parental material in the Mau Forest region, Western Kenya. Native forest topsoils (0-5 cm) had a bulk density of 1.0 ± 0.2 g cm −3 which was similar to values found for topsoils of forest plantations (1.1 ± 0.2 g cm −3), but significantly lower than topsoils from croplands (1.4 ± 0.2 g cm −3), tea plantation (1.3 ± 0.3 g cm −3) and pastures (1.4 ± 0.2 g cm −3). Similarly, soil infiltration rates were higher in native forest (76.1 ± 50 cm h −1) and in forest plantation (60.2 ± 47.9 cm h −1) than in croplands (40.5 ± 21.5 cm h-1), tea plantations (43.3 ± 29.2 cm h −1) and pastures (13.8 ± 14.6 cm h −1). Native forest had the highest topsoil organic carbon contents (8.11 ± 2.42%) and field capacity (0.62 ±0.12 cm 3 cm −3), while the highest permanent wilting point was recorded for pasture soils (mean of 0.41 ± 0.06 cm cm −3). The highest plant available water capacity was recorded for Changes in land use and land management have a strong impact on soil properties, such as hydraulic conductivity and bulk density (

The aim of this study was to determine the hydraulic properties of Nairobi area in order to highlight the groundwater potential and to identify the distribution of hydraulic characteristics of aquifers in the area as well as to highlight vulnerability of the aquifer to heavy abstraction. Documented pumping tests data of boreholes located in Nairobi County were analyzed. Pumping test data from eighty four (84) single-well boreholes were analyzed in AQTESOLV software to determine transmissivity and storativity using Cooper-Jacob's, Theis's, Papadopolus-Cooper's and Theis's recovery methods. Hydraulic conductivity was calculated based on the relationship between hydraulic conductivity and transmissivity. The values of transmissivity for all wells ranged between 1.11 and 360.58 m²/d by using Theis -and Cooper-Jacob methods, 1.10 and 360.58 m²/d by Papadopulos-Cooper method and between 1.289 and 677.81 m²/d by Theis recovery method. The city of Nairobi faces increasing ground-water demand due to ever rising population which is mainly driven by rural-urban migration and industrial growth. Surface water has not only been over-stretched but also heavily polluted and unreliable thus groundwater is the only reliable alternative source of water in the area. Lava and pyroclastic formed during Cenozoic age make up the geology. Under these lavas and pyroclastic rocks lie schists of Precambrian age and gneisses of Mozambique belt of the same age. These results indicate that the aquifer is heterogeneous and that the groundwater supply for local water supply (small communities and plants) is reliable but withdrawal for great regional supply is limited.