Nitrate Pollution Risks

Overview

Pollution sources

• Domestic sewage has high loads of nitrogen plus a high water content which both contribute to an effective seepage into groundwater. The recharge areas of the important aquifers (Cenomanian and Pleistocene) are located in the populated uplands; and only few of those urban areas have sewage collection and treatment facilities. The sewage from villages in the Jordan Valley pollutes the upper soil layers that have connections to the shallow groundwater in the alluvial soils (e.g. Wadi Nar sewage river).
• Agriculture is an important risk factor: chemical fertilizers release much nitrogen that moves into the shallow groundwater in the valley. Currently, about 8.600 t of nitrogen are applied annually to the soil in the Jordan Valley through chemical fertilizers, another 1.500 t might be released through irrigation with nitrate-containing water, and 1.000 t might come from organic fertilizers. It is estimated that alone from chemical fertilizers 2.400 t nitrogen per year would leach into the deeper soil layers, and – if the water table is high enough – into the groundwater.
• Dumping sites contain only limited nitrogen and contain little water, so very little nitrogen will be washed out to soil layers or the groundwater. However, the many uncontrolled dumpsites (e.g. the Za'tara and Aleibadeiya waste dumps) are major risk factors for other (toxic) pollutants.
• Industry is less important source for nitrogen pollution but is an important source other toxic pollutants such as hydrocarbons.
• Tourism waste generation and sewage is currently low but might become more important in the future.

Risks for groundwater

• The nitrogen pollution risk for the Cenomanian aquifers in the west of the River Jordan stems mainly from domestic wastewater and sewage in the populated centers that are located in the re-charge areas outside of the Jordan Valley in the uplands (particularly the Jerusalem-Ramallah area).
• The deep mountain aquifers on the east of the River Jordan – for which hardly any data have been available – might show similar characteristics.
• The nitrogen pollution risk for the Pleistocene aquifers in the west of the River Jordan is even higher because they are located above the Cenomanian layers, and they might have direct connections to the Jordan Valley floor. The pollution sources for the Pleistocene aquifers are sewage from villages and towns, dumping sites, and agricultural fertilizer application.
• The nitrogen pollution risk for the shallow groundwater in the valley depends on the movement of nitrogen down the soil to the water table. The pollution sources are much closer to the groundwater: sewage, dumping sites and fertilizer leaching.

Nitrogen transport from the soil surface to the groundwater will be particularly high in areas where sewage is discharged. Springs located groundwater-downstream of towns have higher nitrate concentrations than other springs. For agricultural areas the leakage depth of irrigation water is about 10-50 cm per year which is low compared to most groundwater tables. Thus the risk for the shallow groundwater under agricultural areas is considered lower than for groundwater below built-up areas. Hot spots of nitrogen leakage from agriculture are areas with high-irrigation crops and shallow groundwater such as banana crop areas in wadi fans or along perennial rivers such as Wadi Far’a.

Example results

Qualitative spatial nitrate pollution risk analysis map

Sewage generation and treatment in the Bet Shean region

Nitrogen load map

Nitrate levels in spring water around population centers

Download options

• Risk Modeling Report (in PDF): Loibl W, Orthofer R (2002): Spatial Risk Modeling for Water Shortage and Nitrate Pollution in the Lower Jordan Valley; ARC Seibersdorf research Report, ARC--S-0162, 56 pp., February 2002