5.1. INTRODUCTION
Sustainable management of water resources in the twentyâfirst century faces significant challenges that crosses political, administrative, economic and ecological boundaries. Water can be a critically limiting element to socioâeconomic development, especially in semiâarid and arid regions where the resource is limited (Feng et al., 2018; Mycoo, 2018). Globally, river basins are vulnerable to anthropogenic pressures like population growth (Falkenmark and Molden, 2008; Wang et al., 2018), climate change and variability (Meko et al., 2007; Overpeck and Udall, 2010), agricultural pollution, urbanization, and unsustainable water resources management practices. All these factors pose challenges to sustainable water resources management (Vadiati et al., 2018). The challenge to balance water provision and basic human demands with economic development and healthy ecosystems is becoming increasingly difficult (Berggren, 2018). Water is therefore not only the most important substance for sustaining life on earth, but plays an important role in other resources and sectors (Kresmann et al., 2018; Ololade, 2018).
Climate change is a major driver of global environmental change with the potential to have adverse impacts on water quantity and quality, now and in the future (MEA, 2005; IPCC, 2014; World Bank Group, 2016). Climate change adaptation will therefore play an important role in future water resources management (Garrote, 2017). There is therefore a need to explore methods for assessing the impacts and adaptation measures in relation to water resources management. The revolution that took place in the water resources management sector over the last century called for the development of new tools and approaches to address new challenges associated with complex water systems, including economic analyses related to water resources (Garrote, 2017). Considering the uncertain climate and cumulative impacts thereof, on water resources in the future, more creative problem solving and management strategies are needed.
Assessing sustainability at a geographical scale requires that water management strategies include climatological scenarios, which directly influence the amount of water in watersheds (Mattos et al., 2019). Water resources are, however, highly dynamic due to variable meteorological patterns (Mattos et al., 2019). This variability is expected to increase in future and poses a threat to a large portion of the worldâs population in terms of water security (Vörösmarty et al., 2010). The impacts of climate change are already affecting the hydrological cycle at global, regional and local scales (IPCC, 2014), causing hydrological stress in many regions (Barnett et al., 2005; Henriques et al., 2008; Seneviratne et al., 2010; Seager et al., 2013). The sustainability of water resources is not limited to the impact of environmental change on quantity, but also on quality and availability, which are largely dependent on future socioâeconomic scenarios (Garrote, 2017). The alteration of water resources by extreme events due to climate change will consequently have a negative impact on socioâeconomic development. Sustainable development relies on crossâcutting interlinkages ranging from ethical, and socioâcultural, to politicalâeconomic issues (Atampugre et al., 2016). The challenges associated with the sustainable management of water is even more serious in arid and semiâarid regions (Feng et al., 2018), making the waterâclimateâsustainability (WCS) nexus an important topic to review.
Water scarcity, which could be defined as the deficit between water availability and demand without providing for environmental flows (Gu et al., 2017), is already causing competition between water users, resulting in social conflicts. Water scarcity is expected to become more severe in future as climate models project a consistent decrease in water availability, especially in semiâarid regions where the socioâeconomic backbone of the region may collapse due to its overâdependence on rainâfed agriculture (Garrote, 2017). Water scarcity may also occur in water rich regions due to poor water quality (Friesen et al., 2017), and inadequate policies and management strategies that should have secured water for present and future use. Around the globe, countries like the United States of America (Morckel, 2017), Brazil (Dobrovolski and Rattis, 2015) and Iran (Madani, 2014) have experienced water crises mainly due to poor management strategies (Mattos et al., 2019). Even though water demand will increase due to climate change (Nkomozepi and Chung, 2012), socioâeconomic drivers are expected to have the biggest influence on water sustainability (Alcamo et al., 2007; Garrote, 2017). It is, therefore, critical that climate, soc...
