Reservoirs and water management features

Overall vulnerability

Feature(s) assessed:

• Reservoirs and water management
• Water management – weirs, goyts, soughs and millponds

Special qualities:

• Landscapes that tell a story of thousands of years of people, farming and industry
• Vital benefits for millions of people that flow beyond the landscape boundary

Feature description:

Water management features, including reservoirs, dams, weirs, goyts, soughs and millponds, are found across the PDNP, giving an insight into former industries that were once prevalent, as well as the current supply of water to millions of people. Weirs were often created to harness water in millponds to power mills and other industries, and more recently to manage fishing. Soughs were created to provide underground drainage for lead mines which were found across the White Peak. A number of soughs are scheduled ancient monuments. Goyts are channels that were built to carry water, often feeding mills or powering pumps for water management in mines.

Reservoirs are a frequently a prominent feature in the landscape. Within the PDNP, there are 46 reservoirs covering more than 1,100 hectares. 42 of these reservoirs are found in the Dark Peak and four are found in the South West Peak. The largest is Ladybower Reservoir covering an area of 210 ha and holding up to 27.9 million cubic metres of water. Together with Howden and Derwent Reservoirs, this waterbody dominates the Upper Derwent Valley.

Reservoirs were built to provide a constant supply of drinking water to the major conurbations outside of the PDNP, where growing populations created a rising demand for water. While some date back to the 1800s, for example Damflask Reservoir, others were created much later, for example Errwood Reservoir in the 1960s. Severn Trent Water, United Utilities and Yorkshire Water now own and operate most of the reservoirs within the PDNP. Others are owned and operated by the Canal and River Trust, and a few smaller ones are in private ownership. The neo-gothic dams at Howden and Derwent are both Grade II listed.

For an assessment of the vulnerability of reservoirs as a habitat, please see the ‘Reservoirs’ section.

How vulnerable are reservoirs and water management features?

Reservoirs and water management features in the PDNP have been rated ‘high’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables, with a variable current condition, and a moderate adaptive capacity. Increased rainfall could impact on reservoirs and water management features if there is not enough storage or carrying capacity. The risk of flood to areas downstream could damage historic buildings and mills.

As the historic sites cannot be moved or relocated their adaptive capacity is moderate. While repairs or adaption may be possible they may result in the reduction in historic value.

Current condition:

When some PDNP reservoirs were created, villages were lost as buildings were often left in situ and submerged. These historic features become visible again in periods of dry conditions. For example in 1976 and 1995 the lost villages of Derwent and Ashopton that lie under Ladybower Reservoir were revealed. Dry conditions for much of 2018 saw very low water levels again. This attracted a large number of visitors who went out onto the mud banks to see the relics. A small number of people damaged the remains, removing stones and tiles.

The reservoirs also often have strong cultural associations and significance (for example the link to the ‘Dam Busters’ training operations) and act as focal points for tourism and recreation. Many weirs were created on rivers to facilitate fishing and to help provide waterpower to mills or other industrial processes that were located on riverbanks and in valley bottoms. In some areas, these weirs have been removed to allow natural river processes, losing these historic water management features. In other cases historic weirs and mill structures have been replaced with more modern equivalents. Although the original evidence of these water management features can be lost, some historical knowledge remains through archaeological surveys. A number of water courses themselves have also been altered. Historic engineering work has taken place to straighten or deepen channels which has potentially resulted in the loss of historic information.

Some soughs found in the White Peak are in a fragile and unstable condition. A number date back to the 17th century. The impressive Magpie Sough that served the Magpie Mine was driven with high explosives during the 19th century. Some soughs still function hundreds of years after they were driven – others have suffered blockages or collapse and no longer drain water from underground workings.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

If winters become wetter and rainfall increases there could be insufficient storage within reservoirs. This would increase the flood risk to neighbouring sites and downstream areas, damaging historic buildings, mills and water management features. Historic weirs may also be removed to reduce flood risk and create more natural river flows, resulting in a loss of historic fabric. There is also potential for damage to reservoir structures themselves. Data Certainty: Moderate

Historic structures that provide evidence of the industrial past such as soughs are often fragile and unstable. Any increase in storm events and rainfall could lead to damage from hydraulic action. Data Certainty: Moderate

Human behaviour change

Hotter, drier summers could see water levels drop - increasing the exposure of historical features such as submerged villages. This has already resulted in some damage to these features and could increase. Data Certainty: Moderate Hotter drier summers could also see a rise in tourist numbers visiting reservoirs and waterways and this could put pressure on infrastructure. While this may create more opportunities for local businesses, it is unlikely this would have a positive effect on these features. Data Certainty: Low

The expansion of carbon reduction schemes may mean soughs - historic mine drainage - are furnished with micro hydroelectric generators. These could see water diverted or channels modified. These historic features are often fragile and such changes could damage the structure and diminish their archaeological importance. Data Certainty: Low

Wetter winters may see the drawdown of reservoir levels in order to provide storage capacity during high rainfall events. This could cause erosion issues in some areas or potentially damage reservoir infrastructure. (L)

Sedimentation or erosion

Increased rainfall and wetter winters could increase the intensity of erosion and amount of deposition, resulting in damage to some water management structures. This would only be likely to occur along localised stretches of watercourses. These could be monitored along with their proximity to water management features, so adaptation efforts could be targeted. This means that flooding will mainly affect areas that are already susceptible, but during exceptionally large flood events then new areas that are currently rarely impacted could be affected. Data Certainty: Low

Fragile historic structures are at risk from an increased frequency of storm events. The resulting increase in erosion could cause the loss of evidence of our industrial past. Flash flooding in the Yorkshire Dales recently resulted in the loss of water features at an old lead smelting mill (a scheduled monument) demonstrating the vulnerability of these structures. Data Certainty: Moderate

Plantation woodland often found adjacent to reservoirs could be damaged more frequently by wildfire if summers are hotter and drier. The loss of the trees could increase erosion leading to greater siltation with a potential impact on reservoirs and other historic features. Data Certainty: Low

Invasive or other species interactions

Historic structures could be damaged by invasive species such as Japanese knotweed, as well as the growth of trees and scrub if warmer temperatures and increased precipitation lead to longer growing seasons. Data Certainty: Low

Nutrient changes or environmental contamination

The materials used to build some of the water management features, such as limestone in former mill buildings, could be susceptible to increased weathering due to atmospheric changes and higher acid water concentrations. The impact of this is likely to be limited. Data Certainty: Low

What is the adaptive capacity of reservoirs and water management features?

Overall adaptive capacity rating

Historic sites generally have a low adaptive capacity, as they are extremely difficult or usually impossible to relocate. Because there is usually no flexibility to reduce the amount of change they are exposed to, their vulnerability to climate change is higher. Data Certainty: High If features are only damaged and not lost entirely it may be possible to repair or rebuild them, but it is costly and historic value could be diminished, especially by maladaptation. Data Certainty: Moderate However, within the PDNP the features in this grouping are dispersed over a wide area and this increases their adaptive capacity. Certain geographic areas will be more affected than others meaning that the likelihood of at least some features surviving is higher. Data Certainty: Moderate

A number of the historic features are given some degree of protection as they have listed status. This includes both Howden and Derwent Dams. Many of the features associated with water management such as the Masonry Weir at Curbar and the Wardlow Sough at Litton are scheduled monuments. However this is largely protection from human interference and may not help protect them from natural impacts. The Environment Agency provides policy guidelines for weirs - for example their removal, lowering and modification - as well as a review of best practice. Historic England provides policy guidelines for sustainable management of the historic environment. All these factors make sensitive adaptation measures more likely to be better managed on designated sites, but non-designated assets are extremely vulnerable. Data Certainty: Moderate Grants are available from a limited range of sources, and lack of funding will be a problem for many of these features. Data Certainty: Low

Upstream catchment management affects the flood risk of reservoirs and other historic features further downstream. There is significant scope to improve catchment management practices to slow and delay the flow of water from large rainfall events. Historic England also provides information on protecting industrial heritage sites such as mills from flood events, which could provide helpful adaptation information. Data Certainty: Very High

Key adaptation recommendations for reservoirs and water management features:

Improve current condition to increase resilience

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are aimed at improving the condition of the feature at present, therefore making it better able to withstand future changes to climate.

• Water catchment management practices can be targeted at minimising flood risk and peak water flows. This may include increased woodland cover within the PDNP, restoration of blanket bog and sensitive farming practices, as well as drain blocking in headwater regions.
• Ensure surveyed features are included in Historic Environment Records and Selected Heritage Inventory for Natural England (SHINE) datasets.
• Nurture collaborative networks to build capacity for monitoring (e.g. volunteer groups).

Improve current condition to increase resilience: Targeted conservation efforts for important sites and at risk areas

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are conservation measures aimed at those sites that will have the biggest impact for this feature – either because they are particularly important for the feature or because they are most at risk from climate change.

• Research the most suitable adaptations for individual historic sites taking into account their situation and current use. This could include plans or physical barriers to reduce foot traffic, or physical reinforcement for the most valuable features. Care must be taken to avoid maladaptation.
• Undertake regular monitoring (including at landscape scale) of selected sites to identify those likely to be most vulnerable in terms of archaeology and ecology and to document change and help inform interventions where possible.
• Put forward key sites for scheduling.

Improve current condition to increase resilience: Increase structural diversity to improve resilience at a landscape scale

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations focus on increasing the structural diversity of the area or habitat in which the feature is found. This can help to offset the effects of climate change on the feature, as well as to allow it to be in a better position to recover from future climate changes.

• Plantation woodlands in the uplands and those surrounding reservoirs should be managed to reduce erosion and slow run-off. Structural and species diversification with native broadleaved trees should be investigated. Encourage continuous cover forestry – to maintain higher levels of carbon storage and decrease soil losses.