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The Harnham Water Meadows Framework Management Plan - Contents

8. Drowning

8.1 The EA is assisting raising water levels to the hatches. Successful trials on the watering of the SSSI were undertaken during Feb 2008. The water levels are presently maintained too low at the radial gates by Rose Cottage to permit watering of many meadows, except during exceptional winter flows. Much of Martin’s Mead and Sammel’s Acre are examples. Dialogue is maintained with EA relating to re-programming the gates such that levels during much of the winter can be maintained 15 to 20 cm higher than at present.

8.2 The Trust should promote the notion of drowning as beneficial to the river environment, especially in terms of silt and phosphorous reduction in water returned to the main river. These are aspects identified by research and stated by the EA to be a positive influence on water meadow management. Research with Plymouth University is encouraging in respect of sediment and phosphorus trapping.

8.3 Areas may remain un-watered or periodically flooded, bearing in mind:

Areas present differing opportunities for management. There is a possibility of producing additional habitat areas such as for

snipe and dragonflies.

Locations where remedial works are undertaken, particularly Seven Acres (building up the bank of the main carriage) and

damaged bedworks on Martin’s Mead.

A water Transfer Licence may one day be required under the Water Act 2003.

The lower, generally rectangular, part of Seven Acres is capable of being drowned, even when the river is relatively low. The

lower part of that area provides habitat for the Desmoulins Whorl Snail where drains widen out towards the river.

The occurrence of marsh orchids should be noted.

Martin’s Mead outside the SSSI presents similar opportunities to Seven Acres.

River level discussions with Wessex Water, EA and consulting engineers.

8.4 There is a need to decide the priority of meadows for re-instatement (ANNEX VI). For example, it may be that the present state of Seven Acres is appropriate for watering and conservation, yet Ivy Mead may have problems with water levels and access. Sammel’s Acre (the small rectangular area between ‘part of Cooper’s Mead’ and Hussey’s Mead, ANNEX II) and upper Seven Acres are suitable for public demonstration and interpretation. Sill heights on the Eastern Meadows conditions options for drowning.

8.5 The Conference agreed that traditional drowning may be limited or impossible in places while water levels remain low. It was stressed that there may be reasons of biodiversity that restrict the area managed in this way. Nonetheless, Funds from Higher Level Stewardship could well be directed towards smaller control structures. The Trust will take a ‘micromanagement’ approach to areas within the meadows including clearing carriers and the re-instatement of stops. Experience maintained through hydrological management is recorded.

8.6 Perhaps only 20% of the area is 'drownable' for practical operational reasons. As of March 2008, the frequently irrigated areas total about 10%. Inclusion of many ‘high priority’ areas would likely achieve the desired 20%.

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