Desert Research Foundation of Namibia Occasional Paper XX Summer Desertification Programme 12 Water balance, use and management in the Omaruru Basin Authors Amwele Elina Etuhole Ausiku Petrus Ausiku Ashitse Katrina Lugambo Endjala Toivo Haraseb Bernhardt lifo Fillemon Kaaturalsrael Maswabi Rodrick Moses Moses Mweutota Mkwetu Nathinge Isaac Ncube Ntandozenkosi Shaduka Mirjam Ndahafa Siteketa Veronica Thamina Diina Nandjamba Editors I\itana Elina Shekupe, !Ganeb Kenneth, Hamilton Bill, Lundgren Mark, Mling Nadia, Nantanga Komeine, Parr Thomas, Pettersen Silje, Seely Mary, Van Langenhove Guido The imaruru River supports a diverse blend of agricultural activities, urban and rural set! <lents, vegetation and wildlife. Due to the increased water demand and water h rela j problems arising in the area, the 1i Summer Desertification Programme inVf :gated the water balance and management of the Omaruru catchment. The Jmmercial farmers in the upper Omaruru catchment are said to influence river flow to t/ lower catchment through the creation of farm dams. These farmers are reliant on thei lams to supplement borehole recharge, as watering points for their livestock and as', Irist sites for trophy hunting and photo shoots. In this study, a detailed water bale :e for the Omaruru catchment was created from dam surveys and satellite image ana ,is. This technical survey was augmented through a series of interviews with urb; and rural community members, town councils, traditional leaders, government offie is, and game, livestock and irrigation farmers. The udy found that the 71 farm dams in the upper catchment do not significantly affect rive ow in years of average rainfall. However, they are shown to have the potential to influ lce river flow locally on tributaries of the greater Omaruru River and may affect rive' ow in a minor way in years of low rainfall. Decreasing trends in river flow over the pas ,Oyears are more likely a result of variability in long-term rainfall patterns. The perr Jtions regarding water use vary widely depending on location (upstream vs dO\A ;tream) in the catchment. Furthermore, there is little or no water demand mar Jement in the catchment. Individuals seldom know how much water they use and ther are no water metering systems installed to help identify water problem areas. In rura Ireas, water point committees are often disorganised or non-existent. The is the need for a more unified effort to enhance understanding amongst residents in tl catchment regarding trends in rainfall and river flow. Also, there is a need for a syst <lof monitoring and information sharing among basin water stakeholders to steer dev, Jpment in the catchment in a sustainable manner in the face of limited water resr ces. Absl lCt , , , ii Cha er 1. Introduction 1 1. Water in Namibia 1 1.1 Variability and Scarcity of Water 2 1.2 Rainfall and runoff 3 Water Use in Namibia 3 2.1 Domestic water use ·..· · ·.· 4 2.2 Agricultural use 5 2.3 Mining use 6 2.4 Tourism use 6 2.5 Industrial use 6 2.6 Environmental use 6 Water Management in Namibia (Literature Review) 7 3.1 National Water Policy 7 3.2 Population growth 8 3.3 Government institutions involved in national water management. 8 3.4 CBM and Water Point Committees 8 3.5 NamWater '" , 9 3.6 Water controlled areas 9 3.7 Water as an economic good 9 3.8 Losses and water unaccounted for 10 1· Site description of the Omaruru basin 10 4.1 Population 11 4.2 Biomes and vegetation 11 4.3 Riparian forests 11 4.4 Soils 12 Water issues in the Omaruru basin 12 5.1 Commercial Farmers 12 5.2 Major Towns 13 1.' Historical Data River Flow 15 6.1 Records from the Department of Water Affairs, Division of Hydrology 15 Cha, er 2. The Study 17 2 Objectives of the study 17 2 Terms and definitions 17 2. Methods , ,.'" , 18 3.1 Dam census overview 18 3.2 Basin Modelling 19 3.3 Inflow Modelling 19 3.4 Water demands and supplies overview 20 3.5 Vegetation /Infiltration Survey 21 3.6 The interview process 21 Cha! er 3. Results 23 3. Dam census 23 1.1 Topographic map and satellite image analysis 23 1.2 Area/volume extrapolation 24 1.3 Runoff ofthe DWA hydrological stations along the Omaruru catchment.. 24 1.4 Dam Modelling 25 1.5 Dam model interpretation/basin modelling 27 1.6 Infiltration Rate 27 3 Water Demand in the Omaruru Basin 28 2.1 Water demand for the entire Basin 28 2.2 Urban Water Use - Water Consumption 28 2.3 Urban Water Use - Tariff Structure 30 2.3 Communal farming water use 33 2.4 Commercial farming use 34 2.5 Residents 35 2.6 Municipalities and village councils 35 2.7 All groups 35 Chaj er 4. Discussion 36 4 Dam model discussion 36 1.1 Inflow modelling 36 1.2 Dam model interpretation 37 1.3 Rainfall variability 37 1.4 Rainfall and Runoff 39 4.: Discussion of interview results 40 2.1 A critical water situation 40 2.2 Water shortage 40 2.3 Supply problems 41 2.4 Dry boreholes 43 2.5 Maintenance of boreholes 43 2.6 Water quality 43 2.7 Distance to water 44 2.8 Water Point Committees 45 2.9 The cost of water- payment problems 46 2.10 River flow 47 2.11 Invisible dams 47 2.12 Resource management.. 47 2.13 livestock or game 48 2.14 Poaching and theft 48 Chai er 5. Conclusions/Recommendations 49 Chal er 6. References 50 1.1 \ later in Namibia NarY Jia's population, agriculture and industry continue to expand at an ~te. Yet, lith increased production and expansion, the need to manage the col:lntry's already strai ~d water resources must move to the forefront of issues surrounding development. Watr is an important economic commodity without which development cannot proceed. Deci Ions and policy formulation with regard to water management, and implementation of th se guidelines, will effect both current and future development in Namibia. (\ NarY Jia is one of the driest countries in sub-Saharet..,Africain terms of mean annual 2 rainf II. Ninety per cent of the country's total area of 824 272km is classified as desert, arid r semi-arid land. Coinciding with this aridity, Namibia is subject to extreme rainfall varic ,i1itywith mean annual rainfall between zero and 550mm. Namibia uses water from a va ety of sources such as perennial rivers, ephemeral rivers, groundwater, pans and sprir is (Heyns et ai, 1998). The Okavango, lambezi, Kunene, Kwando-Linyanti-Chobe, and )range Rivers along the northern and southern borders of Namibia are the cour -y's only year-round, above-ground water sources. Additionally, none of these river originate inside Namibia, which makes Namibia reliant on foreign water sources. This Jroblem is particularly apparent in the north where more than half of the Namibian POPl 3tion is located and is dependent on water originating in Angola (Heyns et ai, 199E All r ers that originate in Namibia are ephemeral rivers. Ephemeral riverbeds remain dry f r most or all of the year and rivers flow only after strong rainfall in the surrounding cate! nents. These rivers start in the highlands along a central north-south strip in NarY )ia where rainfall, with annual ranges between 200-400mm, is sufficiently high. Furtl =rmore, terrain conditions such as hilly/mountainous landscapes, impermeable geoi, gy with thin surface soils and limited intercepting vegetation favour surface runoff and Irainage. These rivers bring life-giving water, seeds, and sediment to areas of grea ~r aridity and lower production in the south-west (Jacobson, Jacobson and Seely, 199~ Thel are twelve major ephemeral rivers in northwestern Namibia, which support a vast variE {of ecological and economical activities. Ephemeral rivers are not only important to th people living on these rivers, but also to the prosperity of the nation as a whole. Thel water r .J. only supports urban and rural populations, but also wildlife, vegetation, tounTI, mining, communal and commercial farmers as well as Namibia's most impc tant, fastest growing economic centres (Windhoek, Walvis Bay, and Swa Jpmund). However, this heavy dependence of increasingly populated urban areas on e hemeral river water is about to deplete the limited resources of the system. Since thes rivers do not flow year round, it is necessary to construct impoundments to inter ,=pt the floods and to carry water over into dry periods. This infrastructure is expE Isive, however, and results in high losses through evaporation. A more efficient metl Id is to abstract water from underground aquifers where it is readily available. This extrc ;tion from hard-rock or alluvial aquifers occurs in the form of boreholes and wells, whic are constructed at cost and sometimes the water is piped great distances by water supr ers to fulfil the ever-growing needs of the people. Unfortunately, heavy abstraction from these underground sources is frequently not assessed and is probably unsLtainable in many instances. To guarantee sustainable access to this essential resa rce for all Namibians is an enormous challenge that needs to be faced to satisfy Nan- )ia's basic survival, health and economic needs, which are crucial for future devE )pment across all sectors. 1.1.- Variability and Scarcity of Water One )f the several constraining characteristics of Namibia's water resources is that rainf II varies from year to year, including a few years of exceptionally above average rainf II and more years of below average rainfall. It is also variable both between climatic ZOnE and within them.