Applied Water Science (2019) 9:120 https://doi.org/10.1007/s13201-019-0955-3 ORIGINAL ARTICLE Water quality and hydrogeochemical characteristics of groundwater around Mt. Meru, Northern Tanzania Edikafubeni Makoba1,2 · Alfred N. N. Muzuka1 Received: 17 October 2017 / Accepted: 12 April 2019 / Published online: 7 June 2019 © The Author(s) 2019 Abstract Climate change and population growth around Mt. Meru experienced lower availability of water for domestic and agricultural uses. Reduction in quantity of water is compounded by lack of information on water quality which could lead to undesired health risks and agricultural efects when such water is used for irrigation. Thus, major ions from 54 diferent water types (springs, streams, dug wells, boreholes, and lakes) were used to assess hydrogeochemical characteristics and suitability of water for domestic and agricultural purposes. Results showed dominance of the major cation and anion in the order of + + 2+ 2+ − 2− − 2− − − Na > K > Ca > Mg and HCO 3 > CO3 > Cl > SO4 > NO3 > F , respectively. It is revealed that Mt. Meru is the recharge zone. Geology, water–rock interaction time, and climatic conditions control water chemistry. Major freshwater aquifers were found to be fractured mafc volcanics, breccia, and tuf. Lahars, due to their susceptibility to weathering, were found to host groundwater of low quality. The suitability of water for domestic and irrigation purposes was moderate, in order of lakes < dug wells < boreholes < streams < springs. Fluoride was found to be the major natural contaminant afecting water quality for domestic purposes with mean value of 17.6 mg/L, while elevated Na+ (mean = 118 mg/L), K+ (mean = 59 mg/L) − and HCO3 (mean = 390 mg/L) relative to other ions were found to afect water quality for irrigation purposes. In some few − − cases, anthropogenic pollutions were recognized through NO3 and Cl . Keywords Mount Meru · Water quality · Hydrogeochemistry · Groundwater · Major ions · Fluoride Introduction (UNICEF 2015). Majority of population in these areas con- tinue to depend largely on rivers, lakes, ponds, and irrigation Access and provision of safe and clean water to people, canals as their major sources of drinking water (UNICEF which is among human rights, has been a continued aim 2015). Some of these sources are polluted naturally, and globally. Population growth, poverty, and economic instabil- most of them are vulnerable to anthropogenic pollution. ity among countries have been pointed out to be causative Most of the developing countries are facing economic factors toward not achieving goal No. 7 of the Millennium water scarcity (UNOCHA 2010). Tanzania, one among Development Goals (MDGs) particularly (UNICEF 2015; the developing countries is signifcantly facing economic UN 2015). It is estimated that about 11% of the population water scarcity despite having several freshwater sources globally have no access to safe and clean water with a large such as lakes and rivers (Mjemah et al. 2011; Kashai- number of people living in sub-Saharan Africa and Oceania gili 2012; Mashindano et al. 2013; Mtoni et al. 2013). Water supply from these potential sources to rural and urban areas is still at low scale. In the year 2015, Tan- * Edikafubeni Makoba [email protected] zania was still among the few countries with lowest cov- erage in accessing an improved drinking water sources Alfred N. N. Muzuka [email protected] and sanitation (Kashaigili 2012; Mashindano et al. 2013; UNICEF 2015). The water demand is currently increasing 1 Department of Water, Environmental Sciences due to both population growth and climate change (Mje- and Engineering, Nelson Mandela African Institution mah et al. 2011, 2012; Kashaigili 2012; Mashindano et al. of Science and Technology, P.O. Box 447, Arusha, Tanzania 2013). Due to these factors, there is a positive trend toward 2 Department of Physical Sciences, Sokoine University utilization of groundwater as the main water source for of Agriculture, P.O. Box 3038, Morogoro, Tanzania Vol.:(0123456789)1 3 120 Page 2 of 29 Applied Water Science (2019) 9:120 domestic purposes (Mjemah et al. 2011; Kashaigili 2012; The study area Mtoni et al. 2012, 2013). Anthropogenic activities are pronounced in both urban Location, topography, and climate and rural areas. In urban areas, contamination is mainly attributed to industrial activities and onsite sanitation Meru district is among the districts of Tanzania situated (Mjemah et al. 2011; Napacho and Manyele 2010; Elisante along the Eastern branch of the East Africa Rift System, and Muzuka 2015, 2016a, b) where as in sub-urban to in the northern part of Tanzania (Fig. 1). The topogra- rural areas it is mainly caused by agriculture activities phy varies from ~ 860 m in the southern parts to 4565 m (Bowell et al. 1996; Nkotagu 1996a, b; Bowell et al. (peak of Mt. Meru which is the second highest mountain 1997; Mohammed 2002; Mjemah et al. 2011; Napacho in Tanzania (Fig. 1). The area is characterized by steep and Manyele 2010; Elisante and Muzuka 2015, 2016a, b). slope toward the peak of the mountain and very gentle Fluoride is one among the natural contaminants in ground- slope in the southern parts (Fig. 1). Its climate is signif- water systems which are common in volcanic regions of cantly controlled by Mt. Meru which divides the district Tanzania (Nanyaro et al. 1983; Ghiglieri et al. 2010; 2012; into two climatic zones—windward and leeward sides Malago et al. 2017). According to the fuoride groundwa- creating variations in hydrological and hydrogeological ter survey in Tanzania, it was found that 30% of waters processes. The windward side receives high rainfall aver- used for drinking exceed the recommended standard by aging at about 1000 mm per annual (Oettli and Camberlin WHO, 1.5 mg/L(Thole 2013). The most afected zones are 2005) with most of the springs originating on the slopes the areas along the rift system, the central to Lake zone of the mountain (Fig. 1). The leeward zone receives low parts (Malago et al. 2017). For instance, along the rift rainfall: the mean annual rainfall being less than 500 mm system, Nanyaro et al. (1983) reported high concentration (Oettli and Camberlin 2005; Ghiglieri et al. 2012). There of 690 mg/L from Lake Momella (Fig. 2). Since then, high are two groups of lakes surrounding Mt. Meru. The frst fuoride values have been reported in other water sources group is composed of crater lakes of Duluti and Ngurdoto along the rift system (Ghiglieri et al. 2010, 2012; Malago in the windward side of the mountain (Fig. 1). The second et al. 2017). group is the Momella series lakes in the leeward side of Several geological and hydrological studies have been the mountain (Fig. 1) which are believed to have been conducted within the area (e.g., Nanyaro et al. 1983; Dawson formed from the collapse of Mt. Meru (Dawson 2008). 2008; Ghiglieri et al. 2010, 2012). Most of the researches Unlike crater lakes, Momella lakes are alkaline and saline were limited to fuoride (e.g., Nanyaro et al. 1983), some (Ghiglieri et al. 2010). studies were constrained in specifc parts (e.g., Ghiglieri et al. 2010, 2012, northern part of Mt. Meru) and most of them lacked a continuous data set for the whole district that Physiography could integrate all water types from the windward to leeward sides for detailed study of hydrogeochemical characteristics, The population of Meru District Council (MDC) is groundwater evolution and water quality for both domestic 268,144 people (NBS and Ofce of Chief Stastitian Zan- and irrigation purposes. Furthermore, according the Meru zibar 2013). The MDC has a population growth rate of District Council report (MDC 2013, unpublished) and Vye- 3.1% and a population density of 228 inhabitants per Brown et al. (2014), there is high population growth in Meru square kilometer (Meru District Council 2013) which is district leading to rapid expansion of agricultural activities four times higher than the national population density of and increased water demand for domestic purposes. Agricul- 51 inhabitants per square kilometer (NBS and Ofce of tural expansion is associated with application of fertilizers Chief Stastitian Zanzibar 2013). Such population density and therefore likely to cause contamination in both surface is expected to increase pressure on water resources. and groundwater systems. Therefore, this study aimed to Within the study area, there are three agro-ecological characterize all water sources in the area and assess their zones (high, mid, and low) which have been established suitability for domestic and agricultural purposes. It also based on the topography (Fig. 1) and rainfall distribution. intended to gather information on hydrogeological processes The highland zone (~ 1400–1800 m a.s.l) is character- which integrate water types and its evolution. Through this, ized by high rainfall (~ 1000 mm/yr) and high population zones with diferent water types and quality and zones sus- density (Wameru as the dominant ethnical group) (MDC ceptible to rapid signifcant hydrogeochemical changes can 2013). Agriculture is the major economic activity in this be identifed. Such information is also important in water zone. The common practiced crops are cofee, pyrethrum, management plans especially in water allocation for specifc banana, and potatoes. Most of the crops are grown through- uses, protection, and conservation of water resources and in out the year because of water availability for irrigation locating future potential boreholes for domestic purposes. 1 3 Applied Water Science (2019) 9:120 Page 3 of 29 120 Fig. 1 A map of Meru district showing sampling location purposes. In the middle zone (~ 1000–1400 m a.s.l) where irrigation schemes which lead to water scarcity for the rainfall is relatively low (~ 500 mm/yr), both livestock downstream users. The lowland zone (~ 800–1000 m a.s.l), keeping and agriculture activities are practiced.