5. WATER RESOURCES 5.1 Introduction In order for Umgeni Water to fulfil its function as a regional bulk water service provider, it requires a secure and sustainable supply of raw water. The reconciliation between water resource availability and water demands is therefore of primary importance to the organisation and forms an integral part of its infrastructure planning process. Understanding what water resources are available to the organisation both currently and in the future, and what impacts affect the level of assurance from these resources, is key to achieving the balance between supply and demand and in maintaining the assured level of supply required by the customers. The natural climate is the principal determinant of surface water runoff and groundwater. This section describes the climate as experienced within Umgeni Water’s operational area, as well as the possible impacts of climate change on surface water runoff in the Mgeni System. This section also describes the status quo of the water resources, both surface and groundwater, within Umgeni Water’s operational area, and mentions future development plans that are significant to the organisation. The water resources are grouped in logical regions as shown in Table 5.1 and Figure 5.1. Finally, a progress note is provided on Umgeni Water’s investigation into the less conventional supply options of wastewater reclamation (re-use) and seawater desalination. 110 111 Figure 5.1 Water resource regions in Umgeni Water’s operational area (KZN DoT 2011; MDB 2016; Umgeni Water 2017; WR2012). 5.2 Climate There are three distinct climatic zones within Umgeni Water’s operational area (Figure 5.2), namely: The Köppen classification Cwb which is the alpine-type climate found in and along the Drakensberg Mountains. The Köppen classification Cfb which is the more temperate summer rain climate of the Midlands region. The Köppen classification Cfa which is the subtropical perennial rainfall characterising the areas along the coast. The mean annual precipitation (MAP) within the Umgeni Water operational area varies between 700 and 1000 mm (Figure 5.3) with most rains falling in summer (October to March), although there are occasional winter showers. The national average MAP is about 450 mm per year. The peak rainfall months are December to February in the inland areas and November to March along the coast. The prevailing weather patterns are predominantly orographic, where warm moist air moves in over the continent from the Indian Ocean, rises up the escarpment, cools down and creates rainfall. Rain shadows occur in the interior valley basins of the major rivers where the annual rainfall can drop to below 700 mm. The spatial distribution of evaporation is shown in Figure 5.4 (A-Pan) and Figure 5.5 (S-Pan). This distribution has a similar pattern to rainfall where a relative high humidity is experienced in summer. There is a daily mean peak in February, ranging from 68% in the inland areas to greater than 72% for the coast and a daily mean low in July, ranging from 60% in the inland areas to greater than 68% at the coast. Potential mean annual gross evaporation (as measured by ‘A’ pan) ranges from between 1 600 mm and 1 800 mm in the west to between 1 400 mm and 1 600 mm in the coastal areas (Figure 5.4). Temperature distribution is shown in Figure 5.6. The mean annual temperature ranges between 12°C and 14°C in the west to between 20°C and 22°C at the coast. Maximum temperatures are experienced in the summer months of December to February and minimum temperatures in the winter months of June and July. Snowfalls on the Drakensberg Mountain between April and September have an influence on the climate. Frost occurs over the same period in the inland areas. The average number of heavy frost days per annum range from 31 to 60 days for inland areas to nil for the eastern coastal area. The mean annual runoff is illustrated in Figure 5.7. The spatial distribution of mean annual runoff is highly variable from the Drakensberg mountain range towards the coastal areas with more runoff generated from the mountains and the coastal areas and lesser generated in the inland regions. 112 Figure 5.2 Climatic Zones (Köppen Classification) (KZN DoT 2011; MDB 2016;113 Umgeni Water 2017; WR2012). Figure 5.3 Mean annual precipitation (mm) (KZN DoT 2011; MDB 2016; Umgeni114 Water 2017; WR2012). Figure 5.4 Mean annual evaporation A-Pan (mm) (KZN DoT 2011; MDB 2016;115 Umgeni Water 2017; WR2012). Figure 5.5 Mean annual evaporation S-Pan (mm) (KZN DoT 2011; MDB 2016;116 Umgeni Water 2017; WR90 in WR2012). Figure 5.6 Mean annual temperature (0C) (BEEH 2001; KZN DoT 2011; MDB117 2016; Umgeni Water 2017). Figure 5.7 Mean annual runoff (mm) (KZN DoT 2011; MDB 2016; Umgeni Water 2017; WR2012). 118 5.3 Umgeni Water’s Climate Change Initiatives The Climate Change and the Water Sector Factsheet (DEA, DWS, GIZ and SANBI 2013) summarises climate adaptation interventions with reference to South Africa’s water planning framework in Figure 5.8. It is shown that, whilst ensuring alignment with all water sector role-players, Umgeni Water as a water board contributes to “coherent planning and flexible services” and “prioritisation and resource allocation”. Figure 5.8 Climate adaptation interventions with reference to South Africa’s water planning framework (DEA, DWA9, GIZ and SANBI 2013: 1). The Climate Change and the Water Sector Factsheet (DEA, DWS, GIZ and SANBI 2013) further identifies the relationship between different role-players at the different scales and how they address resilience to climate change in the water sector (Figure 5.9). It is shown in Figure 5.9 that Umgeni Water’s main contribution is to “water resilience”, which is defined as “water resilience 9 Called the Department of Water Affairs (DWA) in 2013; now referred to as the Department of Water and Sanitation (DWS). 119 builds on integrated planning and is based on water management that responds to hydrological variability” (DEA, DWA, GIZ and SANBI 2013: 2). Figure 5.9 Distinction between medium and long-term planning for water, development and climate (DEA, DWA, GIZ and SANBI 2013: 2). Chapter 10 of the National Water Resources Strategy, Second Edition discusses the Climate Change Response Strategy for water resources in South Africa (DWS, 2013). DWS is currently reviewing the Climate Change Response Strategy for water resources and this is anticipated to be finalised in 2017 (DEA and GIZ 2016: 49). The Draft South Africa National Adaptation Strategy (also anticipated to be finalised in 2017) summarises the climate change response strategy for water resources in Section 5.3 (DEA and GIZ 2016). Identified priorities of direct relevance to Umgeni Water are: “Adaptive Governance and Institutions: Ensure that institutions responsible for water resources management in South Africa incorporate adaptive management responses in the development of their strategies, so that they are able to respond to changing conditions. The engagement of stakeholders in the development of these strategic approaches will provide important support in enabling such adaptive management approaches.” “Assurance of Water Supply: Adopt a low or no regrets approach with regards to decisions about water infrastructure, in the context of climate change, to balance socio-economic considerations with ecological considerations”. “Infrastructure Safety: Address the issue of climate change impacts in the Asset Management Plans of all water sector institutions managing water infrastructure”. “Reconciliation Studies: Integrate climate change into reconciliation studies. This will help ensure that approaches to water demand and supply are determined within the context of climate change, and at a system-wide level”. “Groundwater Assessments: Conduct robust assessments to identify how better use of groundwater (including artificial recharge) can strengthen climate change resilience in South Africa”. (DEA and GIZ 2016: 50) 120 DWS and Umgeni Water acknowledged the impacts of climate change on hydrological variability in 2010 in the KwaZulu-Natal Coastal Metropolitan Area Reconciliation Study (2010) although, at the time of that study, the “results of climate change could not be determined accurately” (DEA, DWS, GIZ and SANBI 2013:67). In 2010, Umgeni Water commenced with research into the impacts of climate change on hydrological variability viz. the Water Research Commission study on the potential impacts of climate change on the Mgeni System (2012). Unfortunately, the high variability of results meant that distinct conclusions could not be drawn on the subject, although the potential for an increase in extreme events (floods and droughts) seems possible. In the past financial year, Umgeni Water has commenced with a project to improve the monitoring of hydrological information since an effective monitoring system will be required to respond to changing climatic conditions. This project included the upgrading of Umgeni Water’s existing Water Resources Management System (WRMS) to a user-friendly decision-support system (Water Resources Management Decision Support System, commonly referred to as WRMDSS) with improved functionality. This project is anticipated to be completed in 2017 and is the precursor to the development of a flood-forecasting system. The development of the flood-forecasting system is being undertaken by Umgeni Water, the South African National Biodiversity Institute (SANBI) and uMgungundlovu District Municipality. The duration of this project is two years and the deliverable is to provide a real-time flood-warning system to alert communities of impending flood events. The design of this system commenced in 2016 and the project is anticipated to be completed in 2019. Umgeni Water is also planning to undertake a project, in the 2017/2018 financial year, to investigate the potential impacts of climate change on future water supply based on (1) the multiple hybrid frequency distribution (HFD) risk approach, and/or (2) the latest long term adaptation scenarios (LTAS) using a more detailed and complex water resources system model.