Effects of Climatic Changes on Surface and Groundwater Resources in the Northwestern Part of Jordan
Abstract
During the last 5 decades precipitation records in Jordan have shown a general decreasing trend. Such decreases have certainly their impacts on the availability of surface and groundwater, on soil moisture contents (green water) and on the surface and groundwater qualities. In this article the impacts of decreasing precipitation on the availability of surface and groundwater will be analyzed. The results show that a decrease in precipitation of 10% will result in the reduction of flood runoff by about 39%, and a reduction in groundwater recharge of 16% in rain rich areas receiving more than 500mm/yr increasing to 59% in areas receiving moderate precipitation of around 300mm/yr.
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Introduction
Precipitation (henceforth ppt) records in Jordan during the last 4-5 decades show a general decrease in the amount of ppt with the passage of time. The study area in the northwestern part of the country (Fig. 1) is a very important part of the country in what concerns surface and groundwater resources. The precipitation trends for that area and for Jordan as a whole are given in Figures (2-5). The main consequences of such decreases are:
1- Reduced flood flows.
2- Reduced groundwater recharge.
3- Reduction in soil moisture content (green water) and shorter periods of soils being wetted.
4- Increases in both surface and groundwater salinities.
These consequences have themselves further implications on discharge of springs, water supply, air relative humidity soil temperature etc.
As a result of all these effects rain fed agriculture will reduce, water supply will decline, existing dams will become over sized and generally investments in many projects will be lost or will reduce in value, with all the socioeconomic ramifications of all the above mentioned impacts.
In this article, the decreases in ppt in the northwestern parts of the country, which receive the highest amounts of ppt and hence the water richest areas in Jordan will be illustrated in the form of time series of representative rain gauging stations. After that, the impacts of the reduction in ppt rates on the quantities of surface and groundwater resource will be elaborated.
Conclusion
Climatic changes are expected to have their rigorous effects on precipitation amount and distribution, air temperature and humidity, which in turn will have appropriate impacts on the surface and ground water resources, soil moisture, water quality and socio-economics.
There are strong indications that climatic changes are affecting the amount of precipitation falling over the northwestern parts of Jordan, which have been showing decreasing trends of precipitation during the last few decades.
Flood runoffs of Wadis will be affected by two mechanisms, namely: first, as a result of runoff amounts being directly proportional to precipitation amounts and second as an indirect result of lower flood runoff/ precipitation ratios inherent in lower precipitation amounts. Such mechanisms will result in a flood runoff reduction in northwest Jordan of 39%, if the precipitation amount decreases by 10%.
The results show also that a decrease in precipitation of 10% will result in a reduction in groundwater recharge of 16% in rain rich areas receiving more than 500mm/yr increasing to 59% in areas receiving moderate precipitation of around 300mm/yr.
Countries in the MENA region should gradually become aware of the climatic processes affecting their surface and ground water resources with all the socio-economics and stability implications on these countries. That may trigger taking the necessary measures to alleviate the negative impacts.
