Groundwater recharge rates and surface runoff response to land use and land cover changes in semi-arid environments

Abstract

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.

Modelling the impacts of grassland to cropland conversion on river flow regimes in Skunk Creek watershed, Upper Midwest United States

“…As mentioned in Section , grassland produces an overall flow regime moderation (e.g., Owuor et al, ; Weaver and Noll, 1935; Schilling et al, ); thus, the Indicators of Hydrologic Alteration (IHA) software (The Nature Conservancy, ) was used to evaluate high‐ and low‐flow regimes in addition to mean flow regimes of grassland–cropland land conversion. SWAT model outputs for the simulated scenarios including the baseline scenario were then processed with IHA software (The Nature Conservancy, ) to compute 10 major streamflow statistics to illustrate low (drought) and high‐flow regimes (flood) and determine the magnitude and duration of annual water conditions at the outlet of the watershed (The Nature Conservancy, ).…”

“…When cultivated cropland are converted from forestland and grassland, ET generally tends to decrease, providing opportunity for more water to percolate down and contribute to groundwater recharge (e.g., Adane, Nasta, Zlotnik, & Wedin, ; Owuor et al, ; Scanlon, Jolly, Sophocleous, & Zhang, ), thus leading to downstream flow moderation. Field experiments demonstrated that grassland depletion contributes to changes in hydrologic processes such as ET, run‐off, soil moisture, and infiltration (Fiedler, Frasier, Ramirez, & Ahuja, ; Li et al, ), which are, in turn, influenced by inherent soil properties, land use and land cover patterns, the initial moisture condition, and rainfall patterns (Agnihotri & Yadav, ).…”

Assessing seasonal land cover dynamics in the tropical Kilombero floodplain of East Africa

“…24 A review of land cover relation to groundwater in Ref. 25 revealed a need for site-specific groundwater monitoring networks due to the highly varied environmental and geological landscapes of Africa. The importance of the land use-groundwater relation is emphasized due to the increased demand for water to meet the needs of the rising population.…”

“…The importance of the land use-groundwater relation is emphasized due to the increased demand for water to meet the needs of the rising population. 25 In this study, analysis of multispectral imagery (RapidEye, Landsat, and Sentinel-2 images spanning from 2013 to 2016) was conducted to map seasonal land cover variability. The selected optical images played complimentary roles as RapidEye has a high spatial resolution but is costly while Sentinel-2 and Landsat-8 data are both freely accessible.…”

Using multiple methods to understand groundwater recharge in a semi-arid area

“…Land-use changes may modify recharge rates and affect groundwater resources (Foley et al, 2005;Lerner and Harris, 2009;Owuor et al, 2016). In many semi-arid regions, there has been the conversion of native forests to agricultural land (Foley et al, 2005).…”