The FAO Water Productivity Open Access Portal (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250m) covers Africa and the Middle East (L1). The national level (100m) covers 21 countries and four river basins (L2). The third level (30m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in-situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall R2 of 0.61, and a root mean square error of 1.04 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The soil moisture content, the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WaPOR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.

Numerous socio-economic activities depend on the seasonal rainfall and groundwater recharge cycle across the Central American Isthmus. Population growth and unregulated land use changes resulted in extensive surface water pollution and a large dependency on groundwater resources. This work combines stable isotope variations in rainfall, surface water, and groundwater of Costa Rica, Nicaragua, El Salvador, and Honduras to develop a regionalized rainfall isoscape, isotopic lapse rates, spatial-temporal isotopic variations, and air mass back trajectories determining potential mean recharge elevations, moisture circulation patterns, and surface water-groundwater interactions. Intra-seasonal rainfall modes resulted in two isotopically depleted incursions (W-shaped isotopic pattern) during the wet season and two enriched pulses during the Mid-Summer Drought and the months of the strongest trade winds. Notable isotopic sub-cloud fractionation and near-surface secondary evaporation were identified as common denominators within the Central American Dry Corridor. Groundwater and surface water isotope ratios depicted the strong orographic separation into the Caribbean and Pacific domains, mainly induced by the governing moisture transport from the Caribbean Sea, complex rainfall producing systems across the N-S mountain range, and the subsequent mixing with local evapotranspiration, and, to a lesser degree, the eastern Pacific Ocean fluxes. Groundwater recharge was characterized by a) depleted recharge in highland areas (72.3%), b) rapid recharge via preferential flow paths (13.1%), and enriched recharge due to near-surface secondary fractionation (14.6%). Median recharge elevation ranged from 1,104 to 1,979 m asl. These results are intended to enhance forest conservation practices, inform water protection regulations, and facilitate water security and sustainability planning in the Central American Isthmus.

In Belgium, IWVA uses Managed Aquifer Recharge (MAR) to recharge the aquifer with treated wastewater generated from the communities to sustain the potable water supply on the Belgian coast. This MAR facility is faced with a challenge of reduced infiltration rates during the winter season when pond water temperatures near 4 °C. This study involves the identification of the predominant factor influencing the rate of infiltration through the pond bed. Several factors including pumping rates, natural recharge, tidal influences of the North Sea and pond-water temperature were identified as potential causes for variation of the recharge rate. Correlation statistics and linear regression analysis were used to determine the sensitivity of the infiltration rate to the aforementioned factors. Two groundwater flow models were developed in visual MODFLOW to simulate the water movement under the pond bed and to obtain the differences in flux to track the effects of variation of hydraulic conductivity during the two seasons. A 32 % reduction in vertical hydraulic gradient in the top portion of the aquifer was observed in winter causing the recharge rates to fluctuate. Results showed that water temperature caused a 30 % increase in hydraulic conductivity in summer as compared to winter and has the maximum impact on infiltration rate. Cyclic variations in water viscosity, occurring because of seasonal temperature changes, influence the saturated hydraulic conductivity of the pond bed. Results from the models confirm the impact on infiltration rate by temperature influenced hydraulic conductivity.

Tropical montane cloud forests (TMCF) are recognized for their capacity to maintain high dry-season baseflow, and a host of other, ecosystem services. Despite their importance, they are endangered with a multidirectional array of land use changes, including conversion to pasture and crops such as coffee, while there are places where forest is being recovered. However, little is known about the effects of this complex dynamic on catchment hydrology. We investigated the effect of land use on rainfall-runoff response in five neighboring headwater micro-catchments in central Veracruz, Mexico, by comparing primary TMCF (PF), young (20 yr-old) and intermediate (40 yr-old) naturally regenerating TMCF (YF and IF, respectively), shaded coffee (SC), and an intensively grazed pasture (IP). We used a 4-year record of high-resolution rainfall and streamflow (10 min) data, collected from 2015 to 2019. These data were analyzed via hydrologic metrics and statistical tests. Results showed no statistical difference in the regulation capacity of high flows after 20 years of natural regeneration, compared to the PF. In terms of baseflow sustenance, our results suggested that PF and IF better promote this hydrological service than the other land uses, although all the catchments showed high mean annual low flows. SC exhibited a high capacity to modulate peak flows comparable to that of PF, and an intermediate capacity to sustain baseflow, suggesting that the integrated functioning of this catchment was largely preserved. Finally, we found that 40 years of pasture management can decrease the soil hydraulic properties in the area, causing a fivefold increase in the peak discharge response, and a much lower baseflow maintenance compared to PF.