## 4 Discussions
Hence, a thorough understanding of these effects and the subsequent changes is required to maintain a sustainable water supply in the arid and semi-arid regions. In response to the growing food demand of an increasing human population, semi-arid regions are experiencing a major conversion of natural vegetation to agricultural land, leading to land exploitation due to agricultural practices [83]. Figure 7 shows the situation of land cover changes over drylands, where some hotspot regions were also experiencing LULCC along with groundwater variations. Some regions in Iraq depend on groundwater for sprinkler irrigation to overcome the issue of less water due to a shortage of rainfall. Before this, groundwater was one of the main sources of freshwater and for domestic uses. Because of this change, many government and private wells have been drilled to use for irrigation [84]. In Syria, during the conflict with ISIS, the dependence on groundwater for agriculture grew at an alarming rate, as ISIS controlled the Euphrates river dam [85]. In many parts of Ethiopia, such as the Shinile catchment found in the Somali regional state, the pastoral and semi pastoral communities travel a long distance in search of water and grazing land. It is largely an arid and semi-arid watershed with a large potential for groundwater which the communities are unaware of [86]. New South Wales in Australia has undergone transitions between pasture/scrubland, vineyard and built-up land [87]. These transitions due to tourism and economic development would affect the groundwater recharge in the region. In Argentina, there is evidence of an increase in groundwater recharge in areas where croplands replaced forests [88]. Some studies also show that land cover changes influence ecosystem water fluxes as well as salinity patterns [89; 90]. It is noted that land cover and groundwater change during the later 2010s is possibly connected with global warming conditions between 2014 and 2019, which are among the warmest years on record, and the year 2020 is likely to become the second warmest year on record ([[https://www.ncdc.noaa.gov/cag/global/haywood/globe/land_ocean](https://www.ncdc.noaa.gov/cag/global/haywood/globe/land_ocean)]([https://www.ncdc.noaa.gov/cag/global/haywood/globe/land_ocean](https://www.ncdc.noaa.gov/cag/global/haywood/globe/land_ocean))). Both GLDAS and FLDAS do provide a suite of outputs over a global domain in order to provide physically consistent and spatially and temporally continuous products that are critical for global dryland studies. In particular, FLDAS has been recommended in hydroclimate studies and early warning applications over areas of Eastern, Southern, and Western Africa [57]. However, in Figure 9, the strong discrepancy between GLDAS and FLDAS for certain areas excludes North Africa from the recommendatory list. The analysis in Figures 10 and 11 shows the modeling biases in cold and dry areas from both FLDAS and GLDAS SSM/ET products, showing that they systematically overestimate the SSM and underestimate the ET, respectively. However, the higher SSM values from models may be due to their soil layer depth being configured as 0-10 cm, while the satellite generally detects the soil moisture at depths of 0-5 cm. A study on the central Tibetan Plateau [91] suggested that the modeling biases were contributed by soil texture and soil organic carbon (SOC) content that alters soil thermal/hydraulic properties, which causes the significant underestimation of the surface soil moisture. The present study also suggested that products retrieved from the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) evidently overestimated soil moisture, indicating that the satellite-based retrieval algorithms must be improved for the cold semi-arid regions. In arid and semi-arid ecosystems, it is still a theoretical and technical challenge to partition ecosystem scale ET fluxes between plant transpiration and soil/canopy evaporation [92].