A Few Thoughts, Impressions and Observations on Water Levels and Small Urban Green Spaces in the Lower Stour Valley
Having just returned from the marsh, thankful to be out of the driving rain, I am enjoying the cosy warmth of my home and relaxing in my favourite chair. I don’t have anything pressing to do, so I’m ruminating on water levels and urban green spaces along the Lower Stour Valley Wildlife Corridor. There are opportunities along the banks of the River Stour, between Wilden Marsh and the River Severn, to investigate, improve if possible, graze where appropriate, and protect if practical, small historic wildlife habitats. In spite of recent brown and green field residential and industrial developments close to the river banks, hidden and isolated small green spaces can and do function as valuable mini nature reserves.
One such green space area is situated along the west bank of the River Stour between Wilden Marsh and Hartlebury Common, at the south end of Wilden Lane (shown on the aerial photograph below). These particular small wetland green spaces are now newly stock fenced and gated nature areas awaiting grazing.
A resource essential to the success and vitality of Wilden Marsh Nature Reserve and Lower Stour Valley wildlife in general is, of course, the relatively short (26 mile long) and often powerful River Stour itself. Flowing from its source in the Clent Hills, the river passes through many industrial towns and settlements on its meandering journey along the valley, eventually winding through Wilden Marsh towards its confluence with the River Severn at Stourport-on-Severn.
Wilden Marsh was drying out and degrading after the river was canalised and its historic weir removed during the 1970s, in an unsuccessful attempt to reduce flooding risks. In 2010 two rock weirs were installed in the Wilden Marsh section of the Stour to increase water levels and help rewet the reserve; these work reasonably well, but there is still not enough water available in my view.
Ditches and sluices control the depth and flow of water through various marsh habitat compartments: some requiring more water than others. Natural springs rise and fall in the swamp, their flow dependent on water table height and an adequate annual rainfall. If the river and brook run low for too long there is potential for excessive marsh drainage. Early this year, for the first time, I dammed the outflow of waters from the northern swamp, ponds and scrapes to help prevent the north marsh drying out too early. Even today, when the marsh appears to be very wet, there isn’t enough water to overflow the sluices that enable drainage to the river. I would rather have too much water on the marsh than too little.
Partial drying of the marsh in spring and summer is a natural and beneficial process, which is initiated by the increasing water demands of the growing season and higher evaporation rates due to rising temperatures. The damp and wet ground conditions are essential to the continuing success of a wide range of rare and common wetland flora. We do experience high rainfall during spring and summer, but consecutive hot and dry summers seem to be occurring more frequently. Since the new weirs were installed, ground conditions are now less extreme. My recent impression is of a River Stour gradually running lower for longer. It’s a sign of the times, perhaps, but should preventative measures be considered and implemented before it’s too late. It might be my imagination, but the large rocks used to create the weirs appear to be sinking into the riverbed under their own weight.
At the end of August/beginning of September, when sap stops rising, the marsh water levels can rise quite quickly and overflow will escape over sluices to drain into the River Stour; it’s December and there is no overflow at the north end of the marsh, and very little from the south and middle marshes. I know it is early days to be making sweeping statements about the marsh drying out, but I have been out on the marsh pretty much every day for many years and am sensitive to subtle changes occurring there.
The video shows pooling overflow from the northern swamp. Although there appears to be a large body of water here, there is not enough to overflow the sluice to the river.
Before industry dominated and poisoned the waters of the Lower Stour Valley with many noxious effluents, its wetlands were likely packed with a wide variety of fauna and flora. The Stour was once a trout stream, and I daresay there were salmon there, too, but the Stour of say the fourteenth century must have been a very different watercourse to the River we see today. Kidderminster was known as “The Bad Lands” because of its inaccessible wet and boggy landscape; it was difficult to move around and its inhabitants were under constant threat from waterborne diseases.
The ground level at Falling Sands Nature Area, where the Stour was once diverted along a leat when the sluices at the historic Falling Sands Rolling Mill dam were closed, suggest that the river level must have been much higher upstream of Hoo Brook to allow water to flow through the leat. A higher upstream water level was a means of storing energy for the rolling mill waterwheels.
Wilden Pool, half a mile downstream, was built to store six million gallons of water to increase the river level when necessary so that barges could travel between Wilden Ironworks, Pratt’s Wharf and Falling Sands Rolling Mill.
Use of the Stour to power waterwheels of early industry necessitated the building of weirs, sluices and leats. Increases in water flow and volume likely deepened the river far beyond that of the Stour – once a trout steam. So salmon are using a watercourse that is vastly different to that ancient trout stream. I’m not suggesting that the introduction of salmon is a bad idea – I’m in favour of it. I know salmon are in the River Stour, because I have seen them. I am concerned that the pursuit of salmon on a budget might compromise Wilden Marsh.
The ‘Salmon in the Stour‘ is a four-year project designed to improve the River Stour and all its tributaries for wildlife and people: a collaboration between Severn Rivers Trust, Environment Agency, Worcestershire Wildlife Trust, and the Wildlife Trust for Birmingham and the Black Country. There are other organisation and groups running projects to improve the River Stour, such as The River Stour Catchment Project, and TransitionsStourbridge.
I wonder about the wisdom of removing too many natural blockages and obstructions from the river and its tributaries and whether doing so will result in a general lowering of watercourse levels. One of the aims of the Salmon in the Stour Project is to increase water flow rates to wash away bottom silt and expose the gravels necessary for salmon spawning. It is also important that fish habitat structures be fixed to the river bed and those of its tributaries. The removal of natural blockages from Hoo Brook a few months ago has resulted in a dramatic drop in the brook water level, which will inevitably lead to the north end of Wilden Marsh drying out still further. I wonder if the requirements of the salmon in the Stour can coexist with the requirements of Wilden Marsh.