Nitrate Water Pollution Risk in the Lower Jordan Valley
243
3.2 Modeling Leakage Depths in the Jordan Valley Floor
The risk for the shallow groundwater in the Jordan Valley floor depends on the
quantity of the nitrogen leakage, and on the leakage depth. The pulse to move
water and pollutant downwards into deeper soil layers depends on the input of
water, climatic conditions, and the soil type. Using an approach of Rowell (1994),
we estimated the leaking depths for the predominantly sandy soils of the valley,
considering soil type, irrigation practices and efficiency, evapotranspiration, and
the lengths of the growing seasons. The results indicate that, with an average soil
moisture content of 5%, the annual leakage depth is between 2 and 7 m (Fig. 5).
As the local water tables are estimated to be in a depth of around 30 m, there is a
considerable risk for groundwater pollution through fertilizer application after
several years of intensive agriculture. The greatest nitrogen leakage risks would
occur in areas with high nitrogen leakage and with shallow water tables, such as
tree cultivation areas near wadi fans or near perennial rivers where the water table
is higher.
4 Summary and Conclusions
With the help of a geographic information system, the interrelations between
origins of environmental risks and destinations of risk receptors can be analyzed
through adjacency or vicinity parameters. The accuracy of the spatial analysis
depends on the quality of the underlying data on the risk factors, and on
appropriate risk parameters.
Because of insufficient available data, the pollution risk for the Cenomanian
aquifer could not be quantified in detail. However, the available data indicate that
there is a considerable nitrate pollution risk through release of nitrogen from
domestic wastewater and sewage, particularly in the densely populated JerusalemRamallah area, which is located directly in the recharge area of the Cenomanian
aquifers. The question whether, where, and how much of the pollutant input will
reach the lower aquifers will require more detailed data about the threedimensional structure of the aquifers, and about the permeability of the bedrock.
Nitrogen pollution risks that affect the Pleistocene aquifers and the shallow
groundwater could be qualitatively estimated through an overlay of risk factors.
The recharge areas of the Pleistocene aquifers cover much of the valley floor and
also the Nablus and Tubas districts. The main risk stems again from domestic
wastewater seepage. The risk from waste dumps and industry is considered much
lower. A severe risk for the Pleistocene aquifer (albeit in an area off the T A) is the
sewage that flows from Jerusalem along the Wadi Nar to the Dead Sea.
Risk of nitrogen pollution for the shallow groundwater in the valley floor
comes equally from the domestic wastewater and sewage, and from the nitrogen
input through fertilizer application and irrigation water. The risk for shallow
groundwater is particularly high around towns and villages. The risks are higher
with increasing population, and with lack of wastewater treatment facilities. There
243
3.2 Modeling Leakage Depths in the Jordan Valley Floor
The risk for the shallow groundwater in the Jordan Valley floor depends on the
quantity of the nitrogen leakage, and on the leakage depth. The pulse to move
water and pollutant downwards into deeper soil layers depends on the input of
water, climatic conditions, and the soil type. Using an approach of Rowell (1994),
we estimated the leaking depths for the predominantly sandy soils of the valley,
considering soil type, irrigation practices and efficiency, evapotranspiration, and
the lengths of the growing seasons. The results indicate that, with an average soil
moisture content of 5%, the annual leakage depth is between 2 and 7 m (Fig. 5).
As the local water tables are estimated to be in a depth of around 30 m, there is a
considerable risk for groundwater pollution through fertilizer application after
several years of intensive agriculture. The greatest nitrogen leakage risks would
occur in areas with high nitrogen leakage and with shallow water tables, such as
tree cultivation areas near wadi fans or near perennial rivers where the water table
is higher.
4 Summary and Conclusions
With the help of a geographic information system, the interrelations between
origins of environmental risks and destinations of risk receptors can be analyzed
through adjacency or vicinity parameters. The accuracy of the spatial analysis
depends on the quality of the underlying data on the risk factors, and on
appropriate risk parameters.
Because of insufficient available data, the pollution risk for the Cenomanian
aquifer could not be quantified in detail. However, the available data indicate that
there is a considerable nitrate pollution risk through release of nitrogen from
domestic wastewater and sewage, particularly in the densely populated JerusalemRamallah area, which is located directly in the recharge area of the Cenomanian
aquifers. The question whether, where, and how much of the pollutant input will
reach the lower aquifers will require more detailed data about the threedimensional structure of the aquifers, and about the permeability of the bedrock.
Nitrogen pollution risks that affect the Pleistocene aquifers and the shallow
groundwater could be qualitatively estimated through an overlay of risk factors.
The recharge areas of the Pleistocene aquifers cover much of the valley floor and
also the Nablus and Tubas districts. The main risk stems again from domestic
wastewater seepage. The risk from waste dumps and industry is considered much
lower. A severe risk for the Pleistocene aquifer (albeit in an area off the T A) is the
sewage that flows from Jerusalem along the Wadi Nar to the Dead Sea.
Risk of nitrogen pollution for the shallow groundwater in the valley floor
comes equally from the domestic wastewater and sewage, and from the nitrogen
input through fertilizer application and irrigation water. The risk for shallow
groundwater is particularly high around towns and villages. The risks are higher
with increasing population, and with lack of wastewater treatment facilities. There