Water Resource Associates
A network of consultants in water resources, water quality, hydrology, hydrogeology and flooding.
Wallers Haven Hydrological study.
The aims of the study were:
to gain a detailed understanding of the water resources of the upland catchment of the Wallers Haven
to assess the impact, of the Haven's augmentation from wells, on the lower catchment's wetlands, the Pevensey Levels.
Background
The Wallers Haven catchment includes the wetlands of the Pevensey Levels, which are designated as an Site of Special Scientific Interest. Since the 1950's wells in the upper catchment have been used to augment both the Haven's summer flows and public water supply abstractions from it. Additionally, drainage ditches have been used by farmers within the Pevensey Levels. Recently there has beeen a degredation of the wetlands.
Study area and boreholes
Scope of work by Water Resource Associates Ltd
The main questions tackled by the study were: Have the flow augmentation and river abstraction reduced the surface and groundwater flow reaching the Pevensey Levels? What is the natural and altered flow regime ? Should the present method of calculation of abstraction be revised ?
Results
A GIS was created of all hydrological data located from the upper catchment. Independent models were made of both the surface and groundwater systems. There was good agreement between the models when used to determine elements of the groundwater flow system. The main conclusions from this were:
- Effects on winter runoff are minimal: 0.040 to 0.060 m3/s lower than natural - difference swamped by flood flows up to 20 m3/s.
- Impact on summer lowflow is positive.
- Deep groundwater seepage is very large in relation to amount abstracted for augmentation.
- Augmentation results in a net annual gain in flow into the Pevensey Levels.