The River Lambourn in East Garston
The Lambourn River normally flows from a spring in Lynch Wood above Lambourn village into the River Kennet near Newbury. The confluence lies quite close to the Hambridge Road turning off the A4, just over one mile east of Newbury. It flows over a total distance of 13 miles and in height it drops from 130 metres above sea level to 75 metres en route. The river, however, is a partial bourne, which means that part of it is likely to dry up for an indeterminate period during the autumn/winter season. The perennial head, where spring-fed water normally flows all the year round, lies below East Garston just to the east of Maidencourt Farm. The system is purely spring fed so that periods of flow are dependent upon the height of the water table, which in turn is largely dependent upon the winter rains.
The Lambourn valley from source to confluence with the Kennet alters in character with distance. Upstream, around Lambourn and East Garston the river flows through rolling open chalk countryside, but lower down the chalk is overlain with deposited sands, clays and gravel, which account for a large incidence of trees with thick undergrowth beyond Welford. These deposits also affect the hydrology in that the clay content restricts the ability of the underlying chalk to absorb rainwater. This means that a more variable regime is enjoyed, in that continuous torrential rain can cause flash flooding.
The chalk is heavily fractured, and it is through these cracks that the water flows and springs develop. Below the chalk is greensand, which also retains water, and below that there is a thick layer of clay which prevents any further water penetration. The springs which develop as a result may feed rivers such as the Lambourn, or they may occur at the boundaries of the chalk on either side of the Berkshire Downs. Most boreholes in the area are sunk into the greensand. This is not a particularly good aquifer, but by sinking boreholes into this level, maximum water abstraction, mainly from the chalk, for that particular site can take place. Most domestic water for the valley is abstracted from a borehole to the west of Lambourn near Ashdown House.
In the event that the water table is much higher than usual over extended periods, springs appear in places which are normally dry. In 1967 and 1999, the Lambourn River itself rose at a point a mile further up the valley at Upper Lambourn. Along its route, there are dry valleys at right angles to the river, but during these periods of high water table, springs in these dry valleys begin to function again. The river is normally sustained, however, by springs along its route, in the bed or banks of the river. In East Garston some are clearly visible in the side creek adjacent to Highbury Cottage in Front Street.
Records show that the river in East Garston has flowed in the same bed since at least the 16th century. It is interesting that, as far as can be ascertained, the main valley road from Newbury to Lambourn has never passed through Front Street or Back Street; the 'top road' has been there for as long as records go back. A good reason for this may well be the river and its tendency to flood on occasion and so block access to further up the valley. . The 'East Garston bypass' could well be one of the oldest in the country.
The Penny Post Guide to "Looking After The River Lambourn"