Spatial assessment of salinity and nitrate pollution in Amman Zarqa Basin: a case study

Intensive use of land resources in arid and semi-arid regions exert serious pressures on groundwater resources and jeopardize further socio-economical developments. The Amman-Zarqa Basin (AZB), the most vital basin in Jordan, is facing recent groundwater deterioration due to a very large increase in water demands for domestic, agricultural, and industrial uses. The objectives of this paper were to quantify the degree of contamination in the basin by evaluating the characteristics, distribution and seasonal variations of two pollution indicators (nitrate concentration and salinity) and to determine the impacts of human activities (land use) on groundwater quality. Based upon long-term data (1970-2005) of groundwater samples collected from 538 wells across the AZB, spatial analyses indicated that both indicators have a strong spatial dependence and are anisotropically distributed. Prediction maps of Ordinary Kriging and Indicator Kriging provided detailed indications of the major and minor sources of pollution in the basin. Inefficient wastewater treatment plants, industrial activities and agricultural practices were responsible for 91, 85, and 25% salinization of nearby wells, respectively. Nitrate pollution had reached 73% above threshold (50 mg/L) in some cases. The temporal analyses estimated the salinity buildup rate to be around 8 x 10(-2) mu S/cm per day, while nitrate buildup rate was estimated to be around 6 x 10(-2) mg/L per day. Remote sensing and spatial analyses helped greatly in groundwater quality assessment not only in providing the environmental status of the AZB but also in delineating the potential of contamination risk zones and their correlation to human activities. Furthermore, the paper suggests some environmental protection strategies that should be adopted to protect the vital groundwater resources of the basin from further deterioration.