Freshwater supply remains limited in West Africa due to lack of operational governance frameworks. In this study, the Water flow and balance Simulation Model (WaSiM) and the Soil and Water Assessment Tool (SWAT) were applied in the Ouriyori catchment (14.5 km², Benin) to assess hydrological ecosystem services (HES) in terms of service flow and service capacity using the ecosystem accounting framework. The modelling exercises indicated satisfactory goodness-of-fit coefficients greater than 75% with an absolute bias of less than 25%. The HES capacity was in general higher than the HES flow for crop and household (surface/groundwater) water supplies, indicating that the catchment can potentially supply more water under optimal storage and management conditions. Positive and negative shifts in service capacities of crop water and household supplies were observed over the simulation period. These significant results can support sustainable interventions in securing water and food productions through increasing HES flow and capacity.

Soil infiltration at a watershed scale is important for understanding and predicting the hydrological process in soil-water-plant systems. This study investigated the effects of land use (LU) conversion on the infiltration rate in the Ouriyori watershed. To that end, in situ infiltration was carried out over the watershed under thirty-six pairs of adjacent cropland-fallow plots using the hood infiltrometer. Saturated hydraulic conductivity (K_s), soil properties, and soil classes were further compared. Results showed a high variability of K_s following the LU classes with a coefficient of variation greater than 60. After data log transformation, the mean values of K_s showed high infiltration and ranged between 2.59 and 2.42cmd⁻¹, respectively, for fallow land and cropland. Thus, K_s was relatively lower in cropland compared to fallow land. Hence, the low infiltration recorded in croplands indicated the degradative impacts of unceasing tillage operations for crop production without crop residue incorporation into the soil during tillage. There was no significant difference in bulk density and soil texture in both types of land use. Considering soil classes, the highest infiltration rate was found in Ferric Luvisol and the lowest rate in Dystric Gleysol, meaning that the high infiltration observed in Ferric Luvisol was due to the abundance of soil macropores. Change in natural vegetation to croplands induced a low infiltration rate and macropore connectivity. Moreover, fallow lands tend to provide water storage capacity through the improvement of mesopores, while soil compaction through agricultural activities reduces soil porosity and therefore soil infiltration. In addition, the paired Students t-test performed on the transformed data was statistically significant, indicating a difference between K_s under cropland and K_s under fallow land. To improve soil and water conservation for crop production as well as for sustainable rural populations livelihoods in the watershed, occasional fallowing may be observed to dampen infiltration hindering soil surface conditions.

This study evaluated the impact of land use and land cover changes on the water balance of the Couffo catchment (Benin) using the Soil and Water Assessment Tool (SWAT). To that end, soil, land uses, hydro-meteorological data including rainfall, temperatures (maximum and minimum), wind speed, solar radiation, relative humidity and discharge data were used as main inputs. To assess the impact of land uses on the catchment water balance, three different land uses (2000, 2006 and 2011) were used. Results showed that from 2000 to 2011, croplands and fallows increased by 34% while the shrub and grass savannahs decreased respectively by 34 and 24%. In addition, agroforestry and gallery forest decreased by 63% and 58% respectively while a rapid increase in settlement. The study outcome suggested that the SWAT provided satisfactory results for discharge with R², NSE, KGE and absolute percent of bias (absPBIAS) ranged between (0.7–0.9), (0.6–0.9). (0.6–0.9) and (5.3–34) respectively. Moreover, the evaluation of land use and land cover changes on the catchment water balance resulted in an increase in annual surface water and water yield, while the groundwater and actual evapotranspiration (ETa) have decreased. Findings of this study may be a great contribution to water resource management in the Couffo catchment. This may contribute to better allocate water for the actual catchment population demand without dampening those of the future generation.

Achieving sustainable agricultural intensification in inland valleys while limiting the adverse environmental impacts and uncertainties related to water availability requires an analysis of the long-term hydrological behavior of the catchment. Such a task is particularly challenging in West Africa and Benin due to the limited availability of climate and hydrological data. This study evaluates the applicability of the lumped GR4J model for simulating streamflow in three inland valleys of the Sudanian zone of Benin (Lower-Sowé, Bahounkpo and Nalohou). Additionally, we test the reliability of satellite-based rainfall data (GPM-IMERG, CHIRPS or GSMAP) in modeling hydrological dynamics in these small catchments. The results demonstrate that the GR4J model is effective in simulating daily discharge in the three inland valleys (KGE > 0.5 during both calibration and validation periods), with particularly interesting performance in mean-flow conditions. The modeling using GPM-IMERG and GSMAP rainfall data shows mitigated results with acceptable performance at Nalohou and less accurate results at Bahounkpo and Lower-Sowé. CHIRPS emerged as the most consistent among the evaluated products, providing a sound basis for reconstructing general trends and seasonal variations in historical streamflow time series. The approach of combining historical CHIRPS data and the GR4J model provides insights and can support decision-making related to water resource management in terms of resource capacity and volume in the study area. Except for Nalohou (KGE = 0.19 with GPM-IMERG data), we observe limitations in predicting high flows with satellite-based climatic data at Bahounkpo (KGE = 0.02 with GPM-IR) and Lower-Sowé (KGE = −0.01 with CHIRPS), where the near-zero KGE scores indicate marginal improvement over a mean-flow benchmark. Future work should explore how hybrid or flexible modeling approaches can improve the accuracy of runoff simulations in inland valleys, particularly for extreme (low- and high-) flow conditions. Additionally, the analysis of the trends of indicators of hydrological alteration (IHA) must be deepened in these important ecosystems, especially under climate and land-use change scenarios.