Sithabile Tirivarombo

The mechanisms of water uptake and retention by desert plants are critical for predicting ecosystem responses to increasing hydroclimatic variability. This study compares seasonal water uptake between Opuntia imbricata and Opuntia phaeacantha, in the Trans-Pecos region of the Chihuahuan Desert (Texas, USA) through the application of stable isotopes of water (δ2H, δ18O), deuterium excess (d-excess) and line-conditioned excess (LC-excess). The centrifugation method was used to obtain stem and soil water, which was compared to event-based precipitation, surface water, groundwater, and tap water isotopic compositions collected between 2023 and 2025. Our results show that cacti stem water isotopes closely follow monsoonal rains, indicating rapid uptake of recent meteoric inputs from the shallow soil layers. In contrast, a strong isotopic offset during the non-monsoon season suggested longer water residence time, strong evapoconcentration, and physiological adaptability. O imbricata exhibited a stronger dependence on monsoonal precipitation inputs, whereas O. phaeacantha demonstrated higher seasonal stability, presumably driven by morphological and storage related adaptations. Our results emphasize the prevailing role of monsoonal rainfall in maintaining cactus ecohydrological functionality and the importance of centrifugation to extract isotopically representative mobile water in succulent tissues and soils.

Improved drought and flood management in semi-arid transboundary basins requires a better understanding of the connections between dry and wet extremes, surface water and groundwater, upstream and downstream, and local communities and formal governance actors. This study describes a multi-disciplinary and mixed-methods research in the Limpopo River Basin, southern Africa. The methodology included hydrometeorological data analysis to identify drought and flood events, group discussions with 240 local community participants about drought and flood processes, impacts and preparedness, and interviews with 36 (inter)national and regional water managers and policymakers about drought and flood governance, early warning and communication. Additionally, we co-created drought and flood management scenarios through transboundary and national workshops and modelled these with an integrated surface water-groundwater model. We found that floods are crucial for aquifer recharge, providing baseflow during droughts, but also impactful for communities, who receive less training and support for floods than for droughts. Flood early warnings (if provided) are often not acted upon because of cultural values or limited resources. Drought and flood adaptation strategies were simulated to be effective, but factors like investment and maintenance costs, technical capacity and community uptake impact implementation. Furthermore, technical measures alone are inadequate to reduce community risk if underlying vulnerabilities are not addressed. Therefore, strengthening connections between communities and formal governance actors and better transboundary management of surface water and groundwater connections could yield significant benefits. Contribution: This study provides 11 distinct recommendations for managing drought and flood risk, focussing on the four connections analysed.

Soil wearing away or erosion is a chief agent of land loss in agricultural land and is regarded worldwide as a serious environmental hazard. This study performed watershed prioritization using morphometric parameters based on fuzzy best worse method (F-BWM) and GIS integration for Gusru Watershed, India. This study prioritizes sub-watersheds of the study area from viewpoint of soil erosion using five major parameters i.e., stream frequency (F_s), relative relief (R_r), length of overland flow (L_o), relief ratio (R_h) and drainage density (D_d). Fuzzy based Best Worse Multi-Criteria Decision-Making (F-BWM) Method was used to assigning weights to used criteria and combining them to achieve erosion susceptibility for each sub-watershed. Results showed that sub-watersheds 9, 14, and 5 were most susceptible to soil erosion and sub-watershed 3 was the least from the viewpoint of soil erosion ranking.

This paper evaluates the impacts of climate change on agricultural droughts in the Zambezi River basin.

The processes that occur in wetlands and natural lakes are often overlooked and not fully incorporated in the conceptual development of many hydrological models of basin runoff. These processes can exert a considerable influence on downstream flow regimes and are critical in understanding the general patterns of runoff generation at the basin scale. This is certainly the case for many river basins of southern Africa which contain large wetlands and natural lakes and for which downstream flow regimes are altered through attenuation, storage and slow release processes that occur within the water bodies. Initial hydrological modelling studies conducted in some of these areas identified the need to explicitly account for wetland storage processes in the conceptual development of models. This study presents an attempt to incorporate wetland processes into an existing hydrological model, with the aim of reducing model structural uncertainties and improving model simulations where the impacts of wetlands or natural lakes on stream flow are evident. The approach is based on relatively flexible functions that account for the input–storage–output relationships between the river channel and the wetland. The simulation results suggest that incorporating lake and wetland storage processes into modelling can provide improved representation (the right results for the right reason) of the hydrological behaviour of some large river basins, as well as reducing some of the uncertainties in the quantification of the original model parameters used for generating the basin runoff. Copyright © 2013 John Wiley & Sons, Ltd.

Sewage discharges and nutrient levels in Marimba River, Zimbabwe