In 2008, The National Trust commissioned Haycock Associates (an environmental consultancy) to investigate the hydrology of the whole Vision area, concentrating on the water demands and supplies, both now and considering future climate change scenarios. A summary of the findings are presented here.

The aim of the Wicken Vision is to create a large, landscape scale mosaic of wildlife habitats, of which wetlands will be a major part. Of particular importance for wetland creation are the remaining peat soils which cover about 44% (2357 hectares) of the Vision area. Maintaining the wetness of the peat areas is key to reducing their loss through oxidation and erosion.

A basic water demand for the Wicken Vision area was calculated using rainfall and temperature data from the Meteorological Office and UK Climate Impacts Programme (future 2020s and 2080s scenarios).

Water balance for the Wicken Vision area:

In common with all of lowland Britain, the water balance shows the area to have an excess of water in winter and a deficit in summer, due to the great increase in evapotranspiration from soils and plants in the summer. Overall, there is an annual water deficit, which is predicted to increase due to climate change. Therefore, if drying of the wetland habitat areas of the Wicken Vision is to be avoided in the summer months, an input of water will be required.

However, the Wicken Vision area is unusual as there are a number of potential water sources in the area and thus proposed wetland habitats are not dependent on rainfall alone for water supply. Also, the peat soils are in the lowest lying parts of the Vision area and it is possible that water from the whole catchment could flow into these parts.

The Swaffham Internal Drainage Board (IDB) drains which run through the whole area remove substantial volumes of water from the system. On average, 9,325,000 m3 of water are pumped annually from the drainage system up into the River Cam. Thus there is sufficient water in this system to meet the water requirements of the peat soils (currently 6,550,000 m3) in the Vision area.

The mosaic of habitats envisaged in the Wicken Fen Vision project are not all wetland. However if wetlands are to be the primary habitat in the peat soils area, then the summer water balance shows that storing winter rainfall somewhere on site is going to be an essential part of the strategy to maintain the wetness of the peat areas during the summer months.

Long dry periods of weather would cause the wetland areas to dry out but an important philosophy of the habitat restoration of the Wicken Fen Vision project is that variations in the rainfall, temperature, grazing regime etc are a natural part of the habitat development. Thus dry or wet years are acceptable.

Soil Carbon of the Wicken Fen Vision area

In 2008, The National Trust commissioned Haycock Associates (an environmental consultancy) to investigate the soil carbon of the whole Vision area. A summary of the findings are presented here.

The intensive agricultural activity, and especially land drainage, across the Wicken Vision area has led to the loss of much of the peat soil through drying, oxidation and erosion. An outline estimate has been made of the amount of soil lost over the last two hundred years due to agriculture. This estimation was based on current land levels (from LiDAR data) and the assumption that the current elevation of Wicken Fen (1.7 mAOD) represents the level to which peat should be present across the area, as Wicken Fen has not been drained.

Total soil loss = 35,948,000 cubic metres.
Equivalent to 27,681,000 tonnes of carbon.

The total loss equates to approximately 101.5 million tonnes of carbon dioxide (CO2). This is equivalent to 780,000 million vehicle km (based on vehicle emissions of 130 g CO2 per km, New Scientist, 2007) or 1.6 times the CO2-equivalent emissions from the UK's entire private vehicle fleet in 2002 (National Statistics 2008).

National Trust land in Burwell Fen
The National Trust owns 208 hectares of low-lying land in the Burwell Fen area. The peat soils in this area were found to average 65 cm in depth, only approximately a third of its original depth due to the many years of drying, oxidation and erosion. Re-wetting this peat soil has the potential for slowing, or even reversing, peat soil loss.

Guidelines for Soil Carbon management