Rivers

Please see below information about the rivers in our Borough.

 

 

Rivers are an important part of our landscape, supporting a diverse range of wildlife and giving pleasure to many. Dinton Pastures has two rivers running through it, the River Loddon, which is the largest and fastest flowing of the two, and the Emm Brook, which flows into the Loddon soon after leaving the park.

The River Loddon rises at West Ham Farm, Basingstoke where it is fed by springs and flows in a north easterly direction to its confluence with the River Thames just west of Wargrave. The Loddon itself is 45.2 km long and descends 47m from the source to its confluence with the River Thames.

 

The total surface area catchment of the Loddon is 1,036 km^{2 _} including the Blackwater sub-catchment - and extends through the counties of Berkshire, Hampshire and Surrey. The map shows the Loddon catchment area and the many tributaries such as the Rivers Blackwater and Whitewater, the Bow Brook and the Emm Brook. The total length of the main rivers in this catchment is 322km.

Chalk underlies much of the Loddon catchment area although it only appears at the surface to the very north of the catchment, near Wargrave, and in the southern most part. Along the course of the rest of the Loddon the chalk lies beneath the Reading beds and London clay. Much of the Blackwater sub-catchment area lies on the sands and clays of the Bagshot, Brackelsham and Barton Beds.

 

The terrace gravels of the Loddon valley have been extracted in a number of places, Dinton Pastures being one of them. When gravel was extracted from Dinton pastures the Emm Brook had to be diverted around the side of the newly formed Black Swan Lake to make way for extraction.

 

The quality of rivers often depends upon how we use them and also how we use the surrounding land. Rivers can be used for a number of purposes:

 

 

The Environment Agency looks after the long-term health of rivers and groundwater. They monitor and assess the quality of rivers with the aim of maintaining and improving water quality. In the Loddon catchment, 206.7 km of river is routinely monitored. The chemical, biological and aesthetic quality of the river is assessed using the General Quality Assessment - GQA - Scheme.

 

 

The chemical quality of a river can be graded as one of six grades, A to F, according to standards of dissolved oxygen, biochemical oxygen demand and total ammonia. The table below shows the distribution of river in the Loddon catchment in each of the six grades since 1993.

 

 

 

Source - Loddon Local Environment Agency Plan, July 2000

 

 

Water quality can also be assessed by measuring the variety and abundance of plant and animal life supported by the river. The Environment Agency routinely monitors the invertebrate life in the river and grades the river using the Biological GQA Scheme. This is a useful assessment as these creatures vary in their sensitivity to levels of pollution and changes in habitat; they are also affected by intermittent pollution that may not be identified through chemical monitoring alone. For more information on river quality assessment contact the Environment Agency.

 

The western part of the Loddon catchment is predominantly rural in character with the exceptions of Basingstoke and Reading. The eastern area, mainly the Blackwater sub-catchment, is predominately urban containing Aldershot, Fleet, Camberley and Farnborough. The Loddon receives treated sewage effluent from two large sewage works, one close to the source at Basingstoke and a second lower down the catchment at Wargrave. The Blackwater receives treated sewage effluent from seven sewage treatment works.

 

Water quality in the Loddon broadly reflects the pattern of urbanisation in the catchment, being of generally better quality (biological and chemical) in the more rural areas to the west. There are very few stretches that are classified as poor quality in the catchment.

 

The Blackwater Valley Project - Blackwater Valley Countryside Project, Ash Lock Cottage, Government Road, Aldershot, GU11 2PS. Telephone 01276 636615 email: blackwatervalley@hotmail.com has now been set up to try and improve the water quality and restore the river corridor back to its natural state. In just a few years improvements can already be seen.

 

Water can only be extracted from rivers and groundwater under licence from the Environment Agency. There are no major river abstractions in the Loddon catchment; the main source of water supply is the underlying chalk aquifer. It is therefore important that the quality of groundwater is maintained and protected from pollution.

 

The Environment Agency's role in the maintenance and management of a healthy river environment is outlined in a document called a Local Environment Agency Plan - LEAP. Such plans also look at the general environment such as waste and air quality. There is now such a plan for the Loddon catchment, which outlines the state of the local environment and identifies issues, which need to be addressed to improve or maintain environmental quality.

 

Where the Loddon passes through Dinton Pastures Country Park the Countryside Service are responsible for looking after the riverbanks and surrounding land. Reed beds are being planted in parts of the park, including some of the Loddon backwaters. This helps to clean drainage water such as road run off before it enters the Loddon and also provides a new habitat; one which is especially good for birds e.g. the Reed Bunting. The Countryside Service is also trying to encourage rare species back to the Loddon within its Biodiversity project. One of these species is the Otter. By building holts - Otter homes - along the riverbank to make up for the general loss of natural holts such as riverside tree roots, we hope that they will eventually return to this end of the river Loddon.

 

The Loddon Valley is recognised as being key to the quality of life in the area. We are currently working on producing a Loddon Valley Strategy to compliment and action the LEAP, ensuring that opportunities to protect and enhance the valley for wildlife and people are maximised.

 

 

Rivers have a limited capacity of water that they can contain and when this capacity is exceeded for example during extreme weather the river floods. When a river floods the water flows onto the surrounding land, called the floodplain which provides a means of storing the excess water, whilst still allowing its continued flow.

 

Traditionally floodplains were important agriculture land as the regular flooding deposited sediment and nutrients creating valuable grazing land. There are many species associated with these damp meadows, making areas of surviving flood plains ecologically important areas.

 

The River Loddon floods into the surrounding land at Dinton Pastures Country Park quite regularly. The meadows alongside the river nearest Woodley, known as the "Wet meadows" are flooded most years and often remain damp through most of the year. The Countryside Service has now re-introduced grazing, the traditional form of management onto the meadows at Dinton Pastures to try and restore the rich diversity of wildlife. The Bader Way, which runs across Mortimers Meadow, is built on mounds, which keep it above the regular flood levels.

 

The ability of floodplains to deal with floodwater is significantly reduced if floodplains are raised, embanked or built upon. This can have serious implications causing flooding in areas where people live. Planning guidelines now carefully control such changes to the floodplains.

 

For more information visit the EmmBrook website.

 

The Environment Agency monitor flood risks and issues flood warnings – contact them for more information on flood risks and management.