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ABSTRACT:
Rainwater harvesting, henceforth RWH, is defined as the system for the collection of water from a catchment area on which rain falls, and storage for later use (Sustainable Earth Technologies, 1999). In arid and semi-arid regions, RWH has been used for several years for many purposes especially in providing water for agricultural and domestic use (Boers et al. 1986; Bruins et al. 1986; Reij et al. 1988; Critchley et al. 1991; Abu-Awwad and Shatanawi 1997; van Wesemael et al. 1998; Oweis et al. 1999; Li et al. 2000; Li and Gong 2002; Ngigi et al. 2005).
In areas such as Palestine, where water resources are scarce, optimal resource management becomes especially essential (Sazakli et al., 2007) For a more sustainable approach, water strategies need to integrate non-conventional resources as part of the national water balance to counter the decrease in reserves while at the same time protect the environment. Rainwater harvesting should be considered an important element to augment water supply to both urban and rural areas while also preventing flooding and alleviating the impact of climate change (Eroksuz and Rahman, 2010; Kim et al., 2005; RiverSides, 2009; van Room, 2007; Villarreal and Dixon, 2005; and Zhu et al., 2004).
Yatta is the study area for this reserch, located 9 km south of Hebron City in the West Bank. The town houses over 100,000 people, 49% of which are females; a population which doubles every 15 years. Yatta has been connected to a water network since 1974 serving nearly 85% of the households. The water network is old and inadequate to meet the needs of the population. The water supply made available to the area is also very limited, estimated to be around 20 l/c.d. Residents are thus forced to rely on water vendors which supply water with a lower quality compared to municipal water while being 400% more expensive. As a cheaper and more reliable alternative, rainwater harvesting is a common practice in the area, with the majority of the households owning at least one cistern. Rainwater harvesting is of great socio-economic importance in areas where water sources are scarce or polluted.
In this research, the quality of harvested rainwater used for drinking and domestic purposes in the Yatta area was assessed throughout a year long period. A total of 100 water samples; were collected from (50 rainfed cisterns) with an average capacity of 69 m3, adjacent to cement-roof catchment with an average area of 145 m2.
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Samples were analyzed for a number of parameters including: pH, alkalinity, hardness, turbidity, Total Dissolved Solids (TDS), NO3, NH4, chloride and salinity. Biological and microbiological contents such as Total Coliforms (TC) and Fecal Coliforms (FC) bacteria were also analysied. Results showed that most of the rainwater samples were within WHO and EPA guidelines set for chemical parameters while revealing biological contamination.
The pH values of mixed water ranged from 6.9 to 8.74 with a mean value of 7.6. collected Rainwater had lower pH values than mixed water ranging from 7.00 to 7.57 with a mean of 7.21.Rainwater also had lower average values of conductivity
(389.11 μScm-1)compared to that of mixed water (463.74 μScm-1) thus indicating lower values of salinity (0.75%). The largest TDS value measured in rainwater was 316 mg/l with a mean of 199.86 mg /l.
As far as microbiological quality is concerned, TC and FC were detected in 99%, 52% of collected rainwater samples, respectively, although they were found in low concentrations. Principal component analysis revealed that microbiological parameters were affected mainly by the cleanness level of catchment areas, while chemical parameters were influenced by human activities.
The research also addressed the impact of different socio-economic attributes on rainwater harvesting using information collected through a survey targeting a statistically representative sample from the area.
Results indicated that the majority of home owners have the primary knowledge necessary to collect and store water in cisterns. Most of the respondents clean both the cisterns and the catchment areas. However, the research also arrives at a conclusion that cleaning is not done in a proper manner. But no matter what the extent to which these households attend to the cisterns, completely eliminating contamination is a near to impossible task.
Results show that a cistern with an operating capacity of 69 m3 would provide sufficient water to get through the dry summer months. However, the catchment area must exceed 146 m2 to produce sufficient water to fill a cistern of this size in a year receiving average precipitation.