NRA Southern 36 THE RIVER MEDWAY National Rivers Authority Nat. Southern Region Infon Guardians of Head C ce the Water Environment Class N o .... 4,.. RWjl widens between Rochester HYDROLOGY THE and Sheerness until the River Medway flows into the Thames Estuary. The Wealden rivers respond rapidly to rainfall and extremes o f RIVER The total length o f the main flow may vary five-hundredfold between summer and winter. Medway from source to the There are six flow gauging stations on the main river, three on the Estuary at Sheerness is 110km River Eden and three on the River Teise. The Eridge Stream, the MEDWAY (70 miles). The river has a Bartley Mill Stream and the Rivers Bourne, Bewl and Beult are also catchment area o f 1400 sq km gauged. above the tidal limit and 402 There are three water supply reservoirs in the Medway catchment, COURSE AND sq km b elow the tidal limit. Bough Beech, W eir Wood and Bewl Water. GEOLOGY HISTORY RESERVOIR VOLUME DESIGN YIELD WATER AREA LOCATION (Ml) (Ml/d) (ha) The River Medway rises in the Ashdown Forest as a spring The name o f the river may Bough Beech 8,630 22.7 113 Tributary of issuing from the Tunbridge derive from a Celtic word, (East Surrey River Eden Wells Sands just above Turners Medu meaning mead, presum­ Water Company) Hill. The sands and clays of the ably signifying a river with High Weald dictate the charac­ “sweet” water. The Romans Weir Wood 5,623 14.1 113 Upper Medway (Southern Water ter o f the river, w hich w ith its called the river Fluminus Services Ltd.) many deeply incised tributaries, Meduwaeias and the Saxons contrasts sharply with the chalk knew it as the Medwaeg. Bewl Water 31,367 76 312 Tributary of streams found in other parts of Historically the importance (Southern Water River Teise the region. The Wealden clays o f the area lay in its relatively Services Ltd.) are impermeable to rainfall and rich and accessible iron water must find its way across deposits. These were exploited the surface of the steeply slop­ on a small scale in the Iron Age Bewl Water near Lamberhurst is the largest reservoir in the ing land, creating a multitude (the grey Wadhurst clay con­ Southern Region and is filled partly by inflow from its natural o f small rushing streams. tains iron nodules or “sows”, catchment and partly by water pumped from the River Teise at These meet to form a typical some with an iron content as Goudhurst. Pumping normally takes place in autumn and winter to Wealden vale as the Medway high as 55% ). In Roman times fill the reservoir for use during the summer. The amount o f water flows north-eastwards towards the ore was heated by charcoal taken from the River Teise is regulated by the National Rivers Penshurst. There, the river is in a clay-walled mound through Authority by a licensing system which ensures that flow does not joined by the River Eden. As it which air was forced by bel­ fall below 23 Ml/d (5 mgd). Releases o f water from the reservoir flows across the Vale of Kent lows. The Ashdown Forest and are used to support Southern Water’s abstraction on the River the gradient is less, though the the High Weald supplied Medway in Maidstone when natural flow in the river is insufficient. river still collects tributaries abundant timber for fuel. After Once river flows are below 352 Ml/d (771/2 mgd), no more water which rise in other parts of the several centuries of decline the may be taken in Maidstone than is being released from Bewl Water. High Weald. These include the industry was revived in Tudor The scheme benefits the River Teise and the River Medway bet­ Rivers Bourne, Teise and Beult. times when the more sophisti­ ween the reservoir and the abstraction point. Mid Kent Water T h e River Teise has m ixed cated blast furnaces introduced Company also uses Bewl Water to supply its treatment works origins; the Upper Teise once by the French were pioneered on site. flowed eastwards to the Rother on the headstreams of the Whilst the largest single abstraction on the river is Southern but was captured by the Lower Medway. W ater’s intake at Maidstone, there are numerous small abstractions Teise when it cut away the soft The process produced cast for agriculture and industry licensed by the NRA. Spray irrigation clay ridge dividing the two iron which was forged into is the major agricultural use particularly on the River Teise and the streams. The River Beult which wrought iron. The steep Weal­ River Beult. rises in the Hythe sandstone den streams proved ideal for Average yearly rainfall in the catchment ranges from 667 mm in ridge is the longest tributary of impounding as “furnace” or the lower Medway to 756 mm in the upper catchment. the river. “hammer” ponds to provide a T h e M edw ay cuts its way head o f water to drive the twin through the Greensand Ridge waterwheels characteristic of beyond Yalding and collects Tudor forges. These drove two more tributaries, the Loose furnace bellows and trip Stream and the River I,en before hammers to forge the iron. reaching the County Town of Another important product Maidstone. The Loose Stream of the Medway Valley was for part of its length flows Kentish ragstone. This was underground. The River Len is quarried by the Romans in the larger and longer, but flows Maidstone area and transported m ore slow ly and has its source to London to build the City near the village o f Ixrnham. walls. The Normans continued L’nlike the tributaries arising in the process, ferrying ragstone the High Weald the Loose and from the Isle of Grain to build Len have more reliable springs the Tower of London. Kentish which sustain their flow through ragstone is still used by the the summer months. National Rivers Authority to Allington Lock forms the build tidal defences. Its w ork­ tidal limit o f the M edway in men continue the traditional Maidstone from whence the skills of shaping the rocks to river flows North, cutting interlock into a durable defence through the chalk. The estuary w ithout the need for mortar. SOUTH EAST ENGLAND TOURIST BOARD Warden Pi arden -■ / / s a in * pt.'f»etAnt> Y* Q ~ > ^ »G«lCUlTU»«il iHOWO*OUM' f l t U j L f ^ j | H ighbro^k "*l Despite low’ dilutions in bel and is an important spawn­ and rain gauges in the catch­ WATER QUALITY summer, the receiving water­ ing ground. Grayling have ment is telemetered to a con­ The National Rivers Authority courses are maintained in Class been stocked to the upper trol room, so that flow through sets objectives for river quality 2. The River Medway itself reaches over recent years and the gates can be regulated. to protect its natural stocks of achieves Class 1A and IB for all some also find their way down Between Leigh and the tidal fish and the uses to which it but an 11.8 km stretch below the River Teise into the River limit at Allington there are ten is put. To achieve these the confluence with the River Medway. navigational locks, and accom ­ objectives, the Authority sets Grom which achieves Class 2. Eels are not so prolific in the panying flood control sluices. limits on all permitted dis­ Historically, the naval base Medway catchment as on the Nine have by-pass channels charges to the river, restricting at Chatham gave great econ o­ Kentish Stour and the River with automatic high capacity their strength and quantity. mic impetus to the lower Rother. In w et years the cx’ca- sluices which maintain a con­ These are known as consent reaches o f the river and its sional sea trout or salmon is stant upstream level and take conditions. estuary. Urban and industrial reported but existing water surplus flows. Six of these have Historically urban develop­ development have been signifi­ conditions in the estuary pre­ radial gates finely balanced by ment and industrialisation cant factors affecting the water vent a self sustaining population a counterweight on the end of have taxed the river’s ability to quality. The principal dis­ from being re-established at an arm. A device with a float­ absorb waste. However, the charges comprise effluents present. like action is attached to the National Rivers Authority and from the paper and chemical arm causing it to tip the — its predecessors have been industries, cooling waters from H G^ u d g e o n * balance when water levels rise. able to bring about improve­ power stations and sewage Bullhead The gate then opens until ments by imposing increasingly effluents from several large water levels fall and the “float” more stringent consent treatment plants. Apart from resumes its original position. conditions. the cooling waters, all effluents Three other sluices have verti­ are treated before discharge to cally operated gates which are QUALITY LENGTH the estuary. CLASS OF RIVER electrically powered. The (km) Motney Hill and Aylesford tenth lock has hand-operated Sewage Treatment Works are rack and pinion, tumbler 1A Water of high quality suitable 23.7 the two largest in Southern Re­ sluices but will be modernised for potable supply abstraction, high class game and coarse fisheries gion with flows o f 42,000 Ml/d in 1991. and 25,900 Ml/d respectively. The NRA sluice and lock IB Water of high quality suitable 312.8 for high class game and Under normal flow condi­ keepers trim levels and operate coarse fisheries tions, effluents are diluted and Allington Lock and the lifting 2 Water supporting good coarse 59.8 dispersed in the tidal waters of bridge at Yalding.