Abstract
In the present study, a 42-year record of rainfall and temperature from Airport and a 43-year rainfall record from Kizimbani meteorological station were analyzed to understand how these climatic variables are affecting groundwater supply on the Island of Zanzibar, Tanzania. Water table fluctuation (WTF) and rainfall data were examined for estimating groundwater recharge. The abstraction volume and recharge rate were used to estimate the water balance. Also, the different physicochemical parameters, such as chlorinity, nitrate, electrical conductivity (EC) and total dissolved solids (TDS) were examined to assess the impact of groundwater pumpage on water quality on the island of Zanzibar. Through the use of WTF method, the present study estimated the recharge rates, local sustainable yield (SY) and integrated water balance (IWB). Rainfall records showed that Zanzibar Island receives a total mean annual rainfall of 1673 mm out of which 7% (equivalent to 1.79 × 106 m3/y) recharges the groundwater. Temperature variations indicated an incremental trend accompanied by low rainfall. The average estimated SY was 0.72%, while the IWB showed a deficit of 39%. Furthermore, the total groundwater abstraction rate in the studied area was 2.49 × 106 m3/y, which was higher than the rate of recharge. This means that the groundwater resources are currently over-exploited and, if immediate action is not taken, the groundwater aquifers may be subjected to pollution, collapse and seawater intrusion. The effects of over-pumping were manifested by high levels of EC, chloride, TDS, total hardness and nitrate that showed an increasing trend with time.
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References
Appelo C, Postma D (2005) Geochemistry, groundwater and pollution, 2nd edn. A.A. Balkema Publishers, New York, USA
Bagheri R, Nosrati A, Jafari H, Eggenkamp HGM, Mozafari M (2019) Overexploitation hazards and salinization risks in crucial declining aquifers, chemo-isotopic approaches. J Hazard Mater 369:150–163. https://doi.org/10.1016/j.jhazmat.2019.02.024
Brears E, Post R (2014) NVCA Water Table Fluctuation Study. Available: https://www.nvca.on.ca/Shared%20Documents/NVCA%20Water%20Table%20Fluctuation%20Study.pdf. Accessed 22 Aug 2019
Bredehoeft JD, Alley WM (2014) Mining groundwater for sustained yield. The Bridge [Online], 44. https://www.nae.edu/111067/Mining-Groundwater-for-Sustained-Yield. Accessed 15 July 2019
Changming L, Jingjie Y, Kendy E (2001) Groundwater exploitation and its impact on the environment in the North China Plain. Water Int 26(2):265–272. https://doi.org/10.1080/02508060108686913
Charman DJ, Barber KE, Blaauw M, Langdon PG, Mauquoy D, Daley TJ, Hughes PD, Karofeld E (2009) Climate drivers for peatland palaeoclimate records. Quart Sci Rev 28(19–20):1811–1819. https://doi.org/10.1016/j.quascirev.2009.05.013
Comte J-C, Cassidy R, Obando J, Robins N, Ibrahim K, Melchioly S, Mjemah I, Shauri H, Bourhane A, Mohamed I, Noe C, Mwega B, Makokha M, Join J-L, Banton O, Davies J (2016) Challenges in groundwater resource management in coastal aquifers of East Africa: investigations and lessons learnt in the Comoros Islands, Kenya and Tanzania. J Hydrol Reg Stud 5:179–199. https://doi.org/10.1016/j.ejrh.2015.12.065
Elias E, Rango A, Smith R, Maxwell C, Steele C, Havstad K (2016) Climate change, agriculture and water resources in the Southwestern United States. J Contemp Water Res Educ 158(1):46–61. https://doi.org/10.1111/j.1936-704X.2016.03218.x
Elisante E, Muzuka AN (2017) Occurrence of nitrate in Tanzanian groundwater aquifers: a review. Appl Water Sci 7(1):71–87. https://doi.org/10.1007/s13201-015-0269-z
Essink GHO (2001) Improving fresh groundwater supply—problems and solutions. Ocean Coast Manag 44(5–6):429–449. https://doi.org/10.1016/S0964-5691(01)00057-6
Gopinath S, Srinivasamoorthy K, Vasanthavigar M, Saravanan K, Prakash R, Suma CS, Senthilnathan D (2016) Hydrochemical characteristics and salinity of groundwater in parts of Nagapattinam district of Tamil Nadu and the Union Territory of Puducherry, India. Carbonates Evaporites 33(1):1–13. https://doi.org/10.1007/s13146-016-0300-y
Haji SH (2010) Water Balance Assessment in Unguja Island, Zanzibar, Tanzania. Master of Science International Institute for Geo-information Science and Earth Observation, University of Twente Faculty of Geo-Information and Earth Observation (ITC), Enschede, Netherlands
Halcrow W (1994) The development of water resources in Zanzibar final report (draft) and appendices to final report. Sir William Halcrow & Partners Ltd, London
Healy RW (2010) Estimating groundwater recharge. Cambridge University Press, Cambridge
Healy RW, Cook PG (2002) Using groundwater levels to estimate recharge. Hydrogeol J 10(1):91–109. https://doi.org/10.1007/s10040-001-0178-0
Idowu TE, Nyadawa M, K’Orowe MO (2017) Hydrogeochemical assessment of a coastal aquifer using statistical and geospatial techniques: case study of Mombasa North Coast, Kenya. Environ Earth Sci 76(12):422. https://doi.org/10.1007/s12665-017-6738-y
Jayathunga K, Diyabalanage S, Frank AH, Chandrajith R, Barth JAC (2020) Influences of seawater intrusion and anthropogenic activities on shallow coastal aquifers in Sri Lanka: evidence from hydrogeochemical and stable isotope data. Environ Sci Pollut Res 27(18):23002–23014. https://doi.org/10.1007/s11356-020-08759-4
Kumar PS (2016) Deciphering the groundwater–saline water interaction in a complex coastal aquifer in South India using statistical and hydrochemical mixing models. Model Earth Syst Environ 2(4):1–11. https://doi.org/10.1007/s40808-016-0251-2
Mato R (2015) Groundwater quality degradation due to salt water intrusion in Zanzibar Municipality. Afr J Environ Sci Technol 9(9):734–740
Mohamed AA, Rahman IA, Lim LH (2014) Groundwater quality assessment in the urban-west region of Zanzibar Island. Environ Monit Assess 186(10):6287–6300. https://doi.org/10.1007/s10661-014-3854-y
Moon S-K, Woo NC, Lee KS (2004) Statistical analysis of hydrographs and water-table fluctuation to estimate groundwater recharge. J Hydrol 292(1–4):198–209. https://doi.org/10.1016/j.jhydrol.2003.12.030
Mountadar S, Younsi A, Hayani A, Siniti M, Tahiri S (2018) Groundwater salinization process in the coastal aquifer Sidi Abed-Ouled Ghanem (Province of El Jadida, Morocco). J Afr Earth Sci 147:169–177. https://doi.org/10.1016/j.jafrearsci.2018.06.025
Mtoni Y, Mjemah IC, Bakundukize C, Van Camp M, Martens K, Walraevens K (2013) Saltwater intrusion and nitrate pollution in the coastal aquifer of Dar es Salaam, Tanzania. Environ Earth Sci 70(3):1091–1111. https://doi.org/10.1007/s12665-012-2197-7
Oiro S, Comte J-C (2019) Drivers, patterns and velocity of saltwater intrusion in a stressed aquifer of the East African coast: Joint analysis of groundwater and geophysical data in southern Kenya. J Afr Earth Sci 149:334–347. https://doi.org/10.1016/j.jafrearsci.2018.08.016
Omar MH (2015) Prevalence of enteric bacteria associated with diarrhea in children less than five years of age and their sensitivity to antibiotics in Unguja Island-Zanzibar. Thesis: Master of Science Department of Life Sciences, The Open University Of Tanzania, Dar Es Salaam
Ponce VM (2007) Sustainable yield of groundwater. http://groundwater.sdsu.edu/gra_0809251330.html. Accessed 10 Oct 2019
Rwiza MJ, Kim K-W, Kim S-d (2016) Geochemical distribution of trace elements in groundwater from the north mara large-scale gold mining area of Tanzania. Ground Water Monit Remediat 36(2):83–93. https://doi.org/10.1111/gwmr.12152
Seward P, Xu Y, Brendonck L (2006) Sustainable groundwater use, the capture principle, and adaptive management. Water Sa 32(4):473–482. https://doi.org/10.4314/wsa.v32i4.5287
Sharpley R, Ussi M (2014) Tourism and governance in small island developing states (SIDS): the case of Zanzibar. Int J Tour Res 16(1):87–96. https://doi.org/10.1002/jtr.1904
Siex KS (2011) Protected area spatial planning for Unguja and Pemba islands, Zanzibar. http://www.coastalforests.tfcg.org/pubs/Protected%20Area%20Spatial%20Planning%20Unguja%20and%20Pemba%20WCS%202012.pdf. Accessed 27 Aug 2019
Sikat LB (2011) Assessing the spatial and temporal characteristics of groundwater recharge in Zanzibar: towards the optimal management of groundwater resources. Thesis: Master of Science Faculty of Geo-Information and Earth Observation, University of Twente, Netherlands
Sophocleous M (2002) Interactions between groundwater and surface water: the state of the science. Hydrogeol J 10(1):52–67. https://doi.org/10.1007/s10040-001-0170-8
Trowbridge C, Critchley A, Ohno M, Largo D (eds) (2006) World seaweed resources—an authoritative reference system. ETI BioInformatics, Amsterdam
Utom AU, Odoh BI, Egboka BC (2013) Assessment of hydrogeochemical characteristics of groundwater quality in the vicinity of Okpara coal and Obwetti fireclay mines, near Enugu town, Nigeria. Appl Water Sci 3(1):271–283. https://doi.org/10.1007/s13201-013-0080-7
WHO (2011) Guidelines for drinking water quality. World Health Organization: Geneva, Switzerland. http://www.iasaude.pt/attachments/article/660/WHO_Guidelines%20for%20drinking-water%20quality.pdf
ZAWA (2017) Preparatory survey on Zanzibar Urban Water Distribution Facilities Improvement Project in the United Republic of Tanzania: final report. Ministry of Lands, Water, Energy and Environment (MLWEE), Dar Es Salaam, Tanzania. https://openjicareport.jica.go.jp/pdf/12302477_01.pdf. Accessed 25 Aug 2019
Acknowledgements
Zanzibar Water Authority (ZAWA) is acknowledged for all valuable information and permission given to do data collection through some selected area on their groundwater source in the urban area. The staff at Zanzibar Airport and Kizimbani meteorological data station are also acknowledged for their support.
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Ali, Z.P., Rwiza, M.J. Assessment of the impact of groundwater pumpage on water supply sustainability in Zanzibar, Tanzania. Environ Earth Sci 79, 490 (2020). https://doi.org/10.1007/s12665-020-09240-8
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DOI: https://doi.org/10.1007/s12665-020-09240-8