Current status of the Ramotswa Transboundary Aquifer Area- Policy Implications P.K. Kenabatho, Ph.D. Department of Environmental Science, University of Botswana, Gaborone. NEPAD Southern African Network of Centres of Excellence in Water Climate Change .. As per UN WATER : Adaptation to Climate Change is mainly about better water management. Without improved water resources management, progress towards poverty reduction targets, the MDGs and sustainable development in all its economics, social and environmental dimensions, will be jeopardized. Population Growth Throughout History (Source: United Nations) Population Growth and Water Availability in the SADC region Water Stress in Many Countries Source: SADC, IUCN, SARDC, World Bank, Sida. Defining and Mainstreaming Sustainability in Water Resources Management in Southern Africa, 2002. p.38 Rainfall pattern, recharge in Southern Africa Spatial variation of rainfall and recharge Complexities of Water Resources Management Reliable supply and Regional good quality Groundwater development resources Reduce Full cost management conflicts recovery Enough Aquifer water at recharge low cost Equal & safe yield access for the poor Industry Policy Makers Water Regional Utilities Water Managers Farmers Groundwater Experts Local NGO Sources of water (Botswana) Indigenous Rivers run for 10-75 days in a year; Recharge Low Inter-basin Transfers Desalination 12 10 8 Extraction rate in 6 Mcm 4 Recharge rate in They drain Mcm annually 2 0 3 Jwaneng N. Orapa Palla Zambesi 2100 Mm Pandamatenga Abstraction and Maun Gweta Masunga Recharge Francistown Shashe Orapa Dikgatlhong Ghansi Letsibogo Selebi Phikwe Charles Hill Serowe Lotsane North-South Carrier Palapye Mahalapye Selika Palla Road Masama Bokaa Riversdale Molepolole Mochudi Jwaneng Mmamashia Sekoma Gaborone Legend Jwaneng Molatedi Kanye Ramotswa Demand Lobatse Surface Source Groundwater Existing Transfer Tshabong Possible Transfer Eastern Botswana Model 2005 Groundwater issues in Ramotswa Evidence of pollution in some aquifers The case of Ramotswa dolomite aquifers One of the boreholes showing high levels of nitrates – largely due to seepage from pit latrines and septic tanks Well field closed in 1996 due to Groundwater pollution Sources of contamination and Water resources mgt issues ü Promotion of use of pit latrines in the 1980s to address sanitation led to grroundwater contamination (Zwikula, 2005) ü Hundreds of private septic tanks were also in use during that time in the industrial complex and railway station in Ramotswa. ü Due to this pollution, the wellfields were decommissioned in 1996 and the village was supplied with water from the Gaborone dam. ü A study done in 2001 indicated that out of 31 boreholes sampled in 2001, 11 had nitrate levels exceeding the Botswana’s recommended quality standards of 45mg/L. Ø Seven of the boreholes sampled in 1983 were re- sampled in 2001 and three of these showed increases in nitrate ranging from approximately 4 times to 55 times (Staudt, 2003). Ø This study also found that about 3000 pit latrines constituted a major groundwater pollution hazard to the shallow water table (where in some cases it is as close as 3m below the ground). Ø Due to increased droughts in recent years, the Water Utilities Corporation (WUC) has rehabilitated the wellfield to augment water supply in the greater Gaborone area as of 2013. Location Map of Ramotswa and Wellfield About Ramotswa Village and Wellfield Ø Ramotswa Village located in South Eastern Botswana, about 25 km south of Gaborone Ø Located closer to two villages, Taung and Boatle Ø Due to its proximity to Gaborone it has experienced significant population growth from 18683 to 23760 between 2001 and 2011 (Statistics Botswana, 2011) Ø Ramotswa wellfield located about 25km upstream of Gaborone dam Ø It covers and area of about 29 km2, part of which is within the village (DWA, 2000) Production boreholes in the area Ø Ramotswa Wellfield comprises 10 production boreholes (4336; 4337; 4340; 4349; 4358; 4373; 4400; 4406; 4422; and 4423) and several monitoring boreholes. Ø Historically, residents of the area draw water from hand- dug wells in the alluvium of the Notwane River. Ø The first recorded early borehole was drilled in 1937. Ø In the late 1970’s, it was decided that groundwater from the dolomites in Ramotswa should be considered for emergency water supply for Gaborone during drought periods. Ø Hence construction of more boreholes and their equipment in the mid 1980s Geology and Hydrogeology The geology in the area consists mainly of three lithological supergroup, i.e. The Otse-Waterberg, The Transvaal, and the Lobatse-Ventersdorp supergroups (Key, 1980, 1983, Carney, et al 1994). The Transvaal supergroup is of greatest hydrogeological importance. Specifically the Ramotswa Dolomite and the Lephala Shales Formation, which are among the highly productive wellfields in Botswana (WUC, 1989). The Lobatse-Ventersdorp supergroup consists of volcano-sedimentary sequences widely distributed in the eastern parts of Botswana, and believed to be 2700 Ma. They are considered to be the oldest in the study area, and belong to the Kaapvaal Craton which forms the Archaean basement over a large area in Southern Africa. This supergroup is predominantly overlain by the Black Reef formation of the Transvaal supergroup. The Ramotswa wellfield extends over an area of 29 km2, which includes part of the Ramotswa Village (Staudt, 2003). The two primary aquifers (Ramotswa Dolomite and the Lephala Shales Formation) are considered to be in local hydraulic connection via the N-S trending fracture zone (Staudt, 2003). The dominant feature of the system is a marked anisotropy associated with high density fracturing In the dolomites groundwater movement is considered to be through local karstification along structural lineaments Leading to high transmissivities and storativities Stratigraphy of the Transvaal Supergroup in the Project area (Key, 1983) Formation Lithology Woodlands Fine-grained silicious rocks Sengoma quartzite Upper massive and pure quartzite; bottom shales Sengoma argillite Upper dolomitic and banded carbonates; bottom shales Ditlhojana quartzite quartzite Ditlhojana volcanic Massive andesites and rhyolites Ditlhojana shale Shales Tsokwane quartzite Massive and flaggy quartzites Lephala Chert clasts, Bevet’s conglomerate Ramotswa shale Siltstones and shale Magopane Bedded chert and minor dolomite Matholobota Inter-layered dolomite and chert Ramotswa Dolomite with minor chert dolomite (stromatolithes) Black Reef quartzite Quartz and pebbles in quartz matrix The dolomites consists of two karst zones: a shallow and deep zone The upper karstic zone has variable thickness of between 20 and 50 m and receives recharge from rivers and percolating rainwater. The deeper karstic zone has a thickness of between 25 to 50 m and recharge is considered to be from South Africa Besides major linear karsts associated with the dolomites, there are also unfractured dolomite country rock which is usually low yielding. Lephala formation is similar to the Dolomites but is unaffected by karstification. It is characterised by two fissured zones which are separated by less fissured zone. The two zones have variable thickness of between 30 to 40m in favour of the upper zone The lower Argillites have better yields at fractured zones which can be at 40-60 m depth Yields of boreholes in the Lephala formation depend on their proximity to the river, intersection of the fissured zone and extent of secondary infills (WUC, 1989, Staudt, 2003). Rivers in the TBA Area The main rivers are Notwane, Metsemaswaane and Taung which are all ephemeral. Notwane River is the main tributary into the Gaborone dam, and flows eastwards towards the Limpopo River. Average rainfall is about 540mm per year Using IWRM best practices to develop Appropriate Capacity and Training to benefit Sub-Saharan Africa Water Security [ACT4SSAWS] AN AFRICAN UNION COMMISSTION RESEARCH GRANT Lead by CSIR in South Africa Involves 7 partners in Southern Africa Undertaking various projects Botswana (UB) dealing with Assessment of Groundwater Contamination in the Ramotswa Aquifer and reduced inflows into the Gaborone dam Snapshots of boreholes in the Aquifer area A Pit latrine located upstream of Inspection of a borehole during and near a borehole in the village a field trip Borehole details BH No. Drilled Screen Water Strike WRL Yield Formation Depth Depth (mbgl) (mbgl) (m3/hr.) (mbgl) (mbgl) 4336 102 Open hole 24-32, 45 14.32 90 Dolomite 4337 118 Open hole 36, 81-82 5.51 90 Shale & dolomite 4340 120 Open hole 13- 7.12 24 Conglomerate 14,30&42 4349 120 12-85 11,37&112 4 90 Dolomite (254mm) 4358 102 Open hole 45 8.05 40 Dolomite 4373 120 (28- 40,56,75&96 7.09 90 Conglomerate 40),(70- 89), (92- 110) 4422 120 Open hole 70-72 4 80 Dolomite 4423 120 Open hole 24-44 6 80 Dolomite Z4400 102 Open hole 47 - 150 Dolomite Water supply from the Aquifer Water is pumped from the 9 production boreholes Not all the boreholes are contaminated, so water from contaminated boreholes are pumped into reservoirs and blended with those from good quality Then treated at nearby treatment plant before it is piped to demand centres (inside and) outside the aquifer area The proposed abstractions from production boreholes is 10,000 m3/day Socio-economic issues-The Case of AU/EU Project(UB)-Contributions from R Chanda and B Mosetlhi ü To investigate the causes of the pollution of the Ramotswa wellfield 1) Factual data and perceptions about the level