Habitat Action Plan

There are approximately 35 chalk rivers and major tributaries ranging from 20 to 90 kilometres in length. They are located in south and east England - from the Frome in Dorset to the Hull in Humberside.

Chalk rivers have a characteristic plant community, often dominated in mid-channel by river water crowfoot Ranunculus penicillatus var pseudofluitans and starworts Callitriche obtusangula and C. platycarpa, and along the edges by watercress Rorippa nasturtium-aquaticum and lesser water-parsnip Berula erecta. They have low banks which support a range of water-loving plants. This plan considers action required for the river channel and banks but not for the whole catchment or floodplain.

All chalk rivers are fed from groundwater aquifers, producing clear waters and a generally stable flow and temperature regime. These are conditions which support a rich diversity of invertebrate life and important game fisheries, notably for brown trout Salmo trutta, brook lamprey Lampetra planeri, salmon Salmo salar, crayfish Austropotamobius pallipes and otter Lutra lutra are among the species listed on Annex II of the EC Habitats Directive which chalk rivers support.

Most chalk rivers have 'winterbourne' stretches in their headwaters. These often run dry, or partially dry, in late summer because of lack of rainfall recharging the aquifer. A characteristic range of invertebrates has adapted to these conditions, as is the brook water crowfoot Ranunculus peltatus.

Where the river corridor (approximately 50m either side of the river) is not affected by intensive agriculture, fisheries or urban development, rich fen vegetation has developed. This is maintained by extensive cattle grazing or naturally progresses to carr woodland. These areas are particularly rich in insect life and breeding birds.

Abstraction: Excessive abstraction mainly for public water supply from the chalk aquifer has contributed to low flows on a number of chalk rivers. This has led not only to drying out of upper sections and riparian zones, but also to accumulation of silt and changes in the aquatic vegetation structure. Artificial measures to counter these effects, such as sealing of the bed with concrete and narrowing of the channel, can themselves have negative ecological consequences.    

Physical modification: Like most lowland rivers, many chalk rivers have had their beds dredged and lowered and have been confined to specific channels for flood defence, drainage, navigation, and other purposes. As 'low energy' systems, chalk rivers have been less able than other river types to reassert their channel structure. Some have side channels, created during much higher flows after the last ice age. These have sometimes been modified to create lakes for ornamental or fishery purposes. The management of water meadows from a mill head was also a familiar practice in recent centuries. The full extent of these modifications on the animal and plant communities of chalk rivers is not known.   

Pollution: In common with most lowland rivers, chalk rivers are significantly affected by sewage discharges and in times of low flow, de-oxygenation may occur. This has caused the upper reaches of at least one SSSI river to be classified in the lowest water quality category. High levels of nitrates (leaching from ploughed land into groundwater) and phosphate (from sewage effluent) are found in many chalk rivers. Because of this enrichment, excessive growths of blanket-weed have been observed on what were previously crystal-clear waters. Changes in plant communities have occurred, including loss of water crowfoot beds from some river stretches. Effluent from fish farms, water-cress beds and light industry can have similar effects.

Fisheries management: On many chalk rivers this is intensive, with regular 'weed' cuts in the channel; fencing off and mowing of strips along the bank; infilling and stabilisation of banks; removal of unwanted fish species (e.g. pike, grayling); and stocking with farm-reared trout. Some fisheries management practices are evidently beneficial to conservation, such as cleaning gravels, while others are neutral providing they do not either impact on characteristic plant and animal communities or are carried out in previously unmanaged areas.

In carrying out their functions the NRA, Water Companies, Internal Drainage Bodies, Local Authorities, in England and Wales have a statutory duty to further conservation where consistent with purposes of enactments relating to their functions. These are set out in the Water Resources Act 1991, and the Land Drainage Act 1991.  River Purification Boards (RPBs) in Scotland do not have the same duties. Both the NRA and RPBs have statutory responsibilities for pollution control.

The duty to further conservation applies to the water management functions of the Environment Agency for England and Wales from April 1996, while the pollution control functions of this Agency will have a duty to have regard to the desirability of conserving and enhancing features of special interest. The establishment of the Scottish Environment Protection Agency (SEPA) and the new water authorities will strengthen conservation duties compared to the predecessor RPBs.

England has the principal resource of chalk rivers in Europe. NE has carried out surveys of river plants on 25 chalk rivers and identified eight (Avon, Frome, Hull Headwaters, Itchen, Kennet, Lambourn, Upper Nar and Test) which qualify as SSSI. These will be notified as statutory sites by 1998. The NRA, Water Companies and local authorities have a duty to further the conservation of all rivers. On SSSI chalk rivers, the NRA has agreed to prepare joint conservation strategies with NE by 1998.

NE has undertaken work to identify which chalk rivers might qualify as SACs under the EC Habitats Directive.

The NRA is undertaking a consultation programme on Catchment Management Plans (CMP) for chalk rivers and plans to publish them by 1998. CMPs include work being undertaken or planned in relation to water pollution control, water resource management, fisheries management and in-river maintenance.

MAFF has designated ESAs in the valleys of two chalk rivers, where farmers are encouraged financially to undertake favourable management and to revert arable to pasture. The Upper Salisbury Avon has also been selected as one of the four pilot rivers for the Water Fringe option of the Habitat Scheme. The Ministry`s Directorate of Fisheries Research has undertaken work demonstrating the problems caused by siltation of spawning gravels and that gravel cleaning can significantly enhance the natural production of juvenile salmonids. Further work is planned on the improvement of spawning gravels and the management of riparian vegetation.

The historical and current contribution of individual riparian landowners in undertaking small scale enhancement works and to some estates for preserving more extensive areas of natural habitat and water meadows alongside these rivers is considerable.

The successful implementation of the action plan will have resource implications for both the private and public sectors. The data in Table 1 below provide a preliminary estimate of the likely resource costs to the public sector in the years 1997, 2000 and 2010, in addition to existing public expenditure commitments in 1995.

The data are based on targets whereby 7000 km of chalk river will be appropriately maintained and improved through to 2010.

Habitat Type: Chalk rivers (£000 per annum)

 

Lawrence Talks, Environment Agency

The following LBAPs are working on Chalk rivers:

Originally published in: Biodiversity: The UK Steering Group Report - Volume II: Action Plans (December 1995, Tranche 1, Vol 2, p238)