Hydraulic gradient, 1950-1999
Developments in hydraulic gradient
The average hydraulic gradient of deeper groundwater in the Netherlands fell in recent decades by more than 30 centimetres (Kremers and Van Geer, 2000).
In the period 1950-1969, the hydraulic gradient fell by approximately 30 centimetres. From 1970 onwards, it appeared to stabilise. From the early nineties onwards, the downward trend seems to have resumed. It is unclear what the reason is for this further fall, and whether it will continue.
Effect of groundwater extraction on the hydraulic gradient
The main reason for the observed fall is the increase in the extraction of groundwater for drinking water and industrial process water. The amount of drinking water extracted rose from about 250 million m3 in 1950 to more than 800 million at present. The amount of groundwater extracted for industrial use was about 300 million m3 in 1950, rising to about 500 million m3 by the early 1970s. It is currently 200 million m3. About 30% of the problems associated with desiccation are due to this increase in groundwater extraction.
Influence of rural land parcelling schemes
Given the increasing scale of agricultural operations, many reparcelling projects and land development schemes have been carried out since the 1950s. Some of the main agricultural objectives of these projects were to improve the hydrological conditions - such as better control over groundwater levels - to prevent flooding and bring in water in dry periods. Approximately 60% of the desiccation problem is caused by this type of measure.
