Management zones in transboundary aquifers: A review of delineation methods under a new framework of cross-border groundwater impacts.

Attention on the use of transboundary aquifers (TBAs) and their cross-border impacts is growing as countries become increasingly concerned about their long-term water security. Cross-border impacts, in groundwater quality and quantity, tend to concentrate in specific parts of TBAs, as they largely depend on the transboundary flow dynamics where anthropogenic actions operate. Thus, there is a growing consensus that strategies intended to prevent or mitigate such impacts should be implemented in strategic zones rather than in the whole TBA. These transboundary groundwater management zones (TGMZs) are relatively recent but have become a prominent topic in TBA management. However, until now, limited effort has been put into exploring the concept of TGMZs and the methods for their delineation. This research aims to fill these gaps and provide a basis for the delineation of TGMZs, thus helping neighbouring countries meet international responsibilities regarding the right to use and enjoy groundwater in TBAs. By reviewing academic and grey literature accessible from public sources, we present an overview of the concept and terminology of TGMZs, the approaches proposed for their delineation, and current operating examples. Additionally, we build a conceptual framework for assessing cross-border groundwater impacts by identifying their typologies and causal factors. We then apply our framework to evaluate and compare three reported methods which identify and delineate TGMZs from distinct perspectives, thereby gaining insights into their principles, performances, and limitations. Finally, we provide recommendations for further research towards optimising methods for delineating TGMZs.

Improving crop yield and water productivity by ecological sanitation and water harvesting in South Africa.

This study quantifies the potential effects of a set of technologies to address water and fertility constraints in rain-fed smallholder agriculture in South Africa, namely in situ water harvesting (WH), external WH, and ecological sanitation (Ecosan, fertilization with human urine). We used the Soil and Water Assessment Tool to model spatiotemporally differentiated effects on maize yield, river flow, evaporation, and transpiration. Ecosan met some of the plant nitrogen demands, which significantly increased maize yields by 12% and transpiration by 2% on average across South Africa. In situ and external WH did not significantly affect the yield, transpiration or river flow on the South Africa scale. However, external WH more than doubled the yields for specific seasons and locations. WH particularly increased the lowest yields. Significant water and nutrient demands remained even with WH and Ecosan management. Additional fertility enhancements raised the yield levels but also the yield variability, whereas soil moisture enhancements improved the yield stability. Hence, coupled policies addressing both constraints will likely be most effective for improving food security.

An African perspective on the Water-Energy-Food nexus.

There is a need to address resource security and distributional justice in developing countries. People need water, energy, and food to sustain their livelihoods, grow economies, and achieve sustainable development. The interactions between these resource sectors form the crux of water-energy-food (WEF) nexus assessments. In this study, we have utilised the WEF Nexus Index to analyse the WEF nexus of 54 African nations. The results from the analysis were used to illustrate the opportunities and constraints for future development. Generally, African countries are performing sub-optimally in the WEF Nexus Index due to the insecurity of water, energy and/or food. The performance of countries varies with context, highlighting the need for contextual analysis in identifying challenges and potential solutions. Implementation of interventions for achieving WEF security needs to be planned from an integrated perspective to optimise synergies and minimize trade-offs. Implementation of the WEF nexus approach towards simultaneous security of WEF resources has potential to improve the WEF nexus. For example and for many African countries, policies that undergird investments in energy supply projects are needed to unlock available freshwater resources and meet food requirements-energy is shown to be a critical enabler of development. Such projects can be utilised to enhance the ability of farmers to manage water through drought-proofing rainfed agriculture, an increase in irrigation development, or both. WEF nexus-based studies, policies, and projects must be focused on the direct and indirect achievement of SDGs 1, 2, 6, 7, and 13, both in terms of access and availability, to ensure distributional justice, especially in the African context. Such actions, combined with broad public participation, can have a ripple effect on other SDGs such as SDGs 5, 10, and 17, thereby reducing inequalities and building partnerships to attain these aspirational goals. The assessment of Africa's relatively low scores in terms of the WEF Nexus Index does not represent a negative narrative. Instead, it provides an entry point to identifying hotspots and understanding the underlying challenges, through which more detailed analyses can lead to identified solutions and policies. Many African countries are trapped in an environment that could be termed a 'poverty-unemployment-inequality nexus' (due to the interlinkages that exist between these 'wicked' problems). The WEF Nexus Index provides high-level insights into these opportunities.

Risk Assessment of Water Quantity and Quality Stressors to Balance the Use and Protection of Vulnerable Water Resources.

In developing regions of the world, valuable and vulnerable water resources are being used excessively. Through water resource development, multiple water quality, flow, and other stressors threaten the sustainable use and protection of these resources. Few attempts have been made to evaluate the synergistic effects of multiple water quality and flow stressors to socioecological attributes of systems that we care about in integrated water resource management. Regional scale ecological risk assessments evaluate the probable negative effects of multiple stressors, affecting dynamic ecosystems on multiple spatial scales. The present study demonstrates how multiple water quality, flow, and other stressors that cumulatively affect the sustainability of the lower Thukela River, South Africa, can be evaluated using the relative risk model, Bayesian network (RRM-BN) approach. This risk assessment facilitated the establishment of minimum water quality and flow requirements to maintain the sustainability of this system and make water resource use and protection trade-off decisions. In this case study, the risk of 10 water resources use and protection scenarios were evaluated in a regional scale ecological risk assessment of the socioecological attributes of the lower Thukela River. In addition we evaluated the consequences associated with these scenarios based on risk pathways of multiple sources, stressors, and receptors to endpoints that represent the sustainable vision of multiple stakeholders of the system. The outcomes of the present study have contributed to new evidence to improve the water resource use efficiency and protect important resources of the lower Thukela River, to ensure sustainability. Integr Environ Assess Manag 2021;17:110-130. © 2020 SETAC.