The Mill River
THE MILL RIVER IS A HIGH ENERGY RIVER SYSTEM
From Buncrana town Rising high above the rural area of Tullydush Inishowen County Donegal and famously mentioned in Lough Swilly Railways commissioned book the land of the lakes the Mill river has been well documented throughout our local history.
The upper area of the Mill River the Owenkillew river there is natural undisturbed areas of nature ,it is not surprising that this area of the river is classified as a Q4-5 water body meaning it is high in water quality a rarity in Ireland now with rivers declining in water quality across Ireland with only a small percentage of Q4-5 water bodies left .
With the upper area of the Mill River being of high Q value status ,the upper Mill river is one of the best places in the Inishowen peninsula to survey and detect a number of high quality macroinvertebrates as well as beautiful conditioned Brown Trout and the amazing and elusive critically endangered European Eel .
The Gransha Dam
The Gransha Dam is located in the mid area of the Mill River catchment ,the dam was constructed to power turbines which supplied the electricity to the townland of Buncrana and for the functioning of the the Working Mill in the lower area of the Mill River catchment known as Swans Mill and also Ranks Mill which gave
employment to Mill workers for many years.
The Gransha Dam ceased operating after the closure of the Ranks Mill and due to no more requirement of the dam to service electricity to the Buncrana townland as the establishment of powerstations had been established.
Today the Gransha dam lays disused state deteriorating year by year, it is seen as an historical part of the history of the Mill river but it also represents a significant barrier to fish migration within the catchment owing to the poorly structured fish pass which has impacted upon the inward and outward migration of fish species notwithstanding the European eels ability to negotiate barriers within river systems.
Our Environment
Local Geology
Buncrana is located on the eastern shore of Lough Swilly in north County Donegal. The main urban area of the town is situated between the Crana River to the north and the Mill River to the south.
The Mill River, south of the town, is crossed by two bridges: Victoria Bridge (known locally as the Iron Bridge) which is the main point of access to the town and the Mill Bridge which is at the end of the Mill Brae road at the south end of the town.
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The underlying bedrock includes Fahan slate formation. The river valley of the Mill River flows over a narrow band of Culdaff limestone with a sill of metadolerite along the river's southern embankment extending from the estuarine zone inland. Sandy gravels and conglomerates overlie bedrock. The geology was formed
during the Lower Carboniferous Period.
The local soils throughout the area range from shallow to moderate depth peaty podzols and established podzolic types with a moderate
percentage of loam and sandy clays.
Soil along the river.
Soil along our river catchments changes in many different areas, the soil along most riverbanks are soft and fertile due to the deposition of silt, sands and gravels a natural part of the river process. You'll see soil around the riverbank after heavy rain and or river spatial flooding event and the soil is very fragile e.g animals grazing near the edge of a river bank or a area use as a means of animals traveling from one place to another.
Or you'll find very soft and fragile, there may be invasive species growing along the river catchment e.g Hymalayan balsam and Japanese knotweed these plants when left untreated can become very deep rooted and will cause loss of ground over time especially with high flooding spates and strong winds.
Domestic Wastewater discharge will damage the river bank soil also leaving high nitrate levels in the water causing eutrophication downstream causing an oxygen deficiency and a loss of river species and biodiversity. Agriculture lands Nitrate and Phosphorus levels can be high in grassland, high phosphate levels can also reduce the hydrological status of our natural water bodies which also impacts upon the species reliant on the natural ecological biodiversity provided by a none polluted river system or lake.
Peatland
Peat soil (bog soil) can be helpful for holding water depending on it being a blanket or raised bogs it's important for drinking water especially here locally in Inishowen, Co. Donegal as it formed a major catchment area of surface water for the likes of leading onto creating large reservoirs for our drinking water, e.g Lough Turk, Illiies ,Buncrana. You can see the Eddie Fullerton Dam originally called Pollan Dam after river Pollan a local tributary running to the 400 acre lake, with the 22.5m cement dam front in place since 1997. This is one of the largest infrastructures owned by Irish water and now carrying water from Buncrana as far as Letterkenny Co Donegal.
The peatlands have a good ground water holding but adequate drainage too after their own plants have enough water, during heavy rainfall and high floods this will make the rivers more acidic and the pH levels can change as all species react to pH to levels if the pH levels are too high or low, the majority of species of our rivers prefer a pH level of 5.5 -9.0 anything over this can e.g cause e.g a fish's gills will thicken and causing oxygen restrictions, the more frequency in the pH levels raising and lowering will cause fish kills along with a veritable amount of species required for our natural river catchment, flora and fauna.