Wildlife Trust Derbyshire Wildlife Trust
East Mill, Bridge Foot, Belper, Derbyshire, DE56 1XH
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E-mail: enquiries@derbyshirewt.co.uk

Royal Derby Hospital
Balancing Pond

Royal Derby Hospital



Derbyshire Wildlife Trust
East Mill
Bridgefoot
Belper
Derbyshire
DE56 1XH
A report for the Wild About Ponds Project
Prepared by Trevor Taylor
Local Wildlife Sites Officer (Planning)
Derbyshire Wildlife Trust

August 2011

Protecting Wildlife for the future

Regisered charity no. 222212
DWT is a company registered in England and Wales
with the Company Number 715675

Royal Derby Hospital Balancing Pond

Background

Derbyshire Wildlife Trust was commissioned to survey the pond located on land to the west of the former Kingsway Hospital in Derby as part of the Wild About Ponds Project in order to provide management recommendations based upon the findings of the survey. It would also enable a comparison of survey results against data obtained as part of the 2004/5 Derby City Pond Survey.

Map 1 shows the location of the pond. The pond is located within a wider area of unmanaged grassland, abandoned arable land and areas of developing scrub to the west of the former Kingsway Hospital grounds. A tall unmanaged hedgerow alongside the A38 road forms the north-west boundary to the site and the Bramble Brook runs alongside the north-east boundary. The pond is within an area defined by post and rail fencing with a locked gate within the fencing allowing access for management.

Habitats immediately surrounding the pond within the site include tall ruderal vegetation along the northern and eastern banks comprising Broad-leaved Dock, Common Ragwort, Creeping Thistle, Common Nettle and Yorkshire-fog, with developing willow scrub at the western end. The steeply sloping south bank is dominated by bramble and tall fen vegetation which is largely impenetrable in places making access along the bank increasingly difficult.

The pond is owned by the Royal Derby Hospital and was created around 2002/3 to act as a water storage facility to collect surface water from the staff car parks. Any surplus water is discharged into the adjacent Bramble Brook via a controlled outfall. The pond was initially surveyed in 2004/5 as part of the Derby City Pond Survey and in the intervening period between the initial and the current survey it would appear that the pond has been expanded to increase its water storage capacity.

There is no public access to the site. Access for the undertaking of the various surveys, which have been carried out since 2004, has been obtained with the kind permission of the Estates Department of the Royal Derby Hospital.

Survey objectives

The aim of the survey was to gather ecological information of the upper waterbody (Allestree West) using the PSYM methodology in order to determine the current overall ecological quality of the pond. An assessment of the ecological value of the lower lake (Allestree East) was also undertaken.

Methodology

The survey followed the standard survey methodology known as PSYM developed by Pond Action (now Pond Conservation) and the Environment Agency. PSYM, the Predictive System for Multimetrics, (pronounced sim) was developed to provide a standard method for assessing the biological qualities of still waters in England and Wales.

The method uses a number of aquatic plant and invertebrate measures (known as metrics) which are combined together and fed into a computer model, along with basic environmental and location data, to obtain a single value which represents the waterbody’s overall quality status.

The recommended time of year for carrying out PSYM pond surveys is during June, July and August. The pond was surveyed during August 2011.

The following information was gathered for the pond:

Calculating the pond metrics

The data collected from the surveys are used to calculate three plant metrics and three invertebrate metrics.

1. Number of submerged and emergent plant species

This is simply the number of submerged plant species plus the number of emergent plant species. The calculation does not include the number of floating-leaved species present. This is because the pond data suggest that the number of floating-leaved plants occurring at a site does not decline significantly with increasing degradation. The metric is therefore improved by omitting this plant group.

2. Trophic Ranking Score (TRS)

TRS is a measure of the average trophic rank for the pond. This is calculated by assigning each plant species with a trophic score based on its affinity to waters of a particular nutrient status. The trophic scores vary between 2.5 (dystrophic, i.e. very nutrient poor conditions) and eutrophic, i.e. nutrient rich conditions).

Unfortunately, not all plants have trophic scores. This situation has arisen because the current TRS values for standing waters (Palmer et al., 1992) are based only on analysis of lake data, and many plant species which are common in ponds occurred at too low a frequency in lakes to give them a score. Also, some plant species exhibit little nutrient preference.

The TRS value for a site is calculated as follows:

  1. The trophic scores from each plant species present at the site are summed together.
  2. The summed score is divided by the total number of plant species which have a trophic ranking score to give the TRS.
3. Uncommon Species Index

Uncommon species are those which have a rarity score of 2 or more. The number of these species is simply summed to give the number of uncommon species.

Uncommon species refers to species which can be best described as "local", "nationally scarce" or "Red Data Book". The rarity status values for Scarce and Red Data Book species are based on existing definitions derived from the Red data Books and other authorities. The definition of "local" has been used to define species which are not uniformly common and widespread in Britain: with plants this refers specifically to species recorded from between 100 and 700 10 x 10 km squares in England, Wales and Scotland.

4. Average Score per Taxon (ASPT)

The ASPT is calculated by summing the BMWP scores for all taxa present at the site and dividing by the total number of BMWP taxa present.

BMWP (Biological Monitoring Working Party) scores are assigned to taxa depending on their known tolerance to organic pollution, a higher score indicating lower tolerance. The scores were defined by Maitland in 1977.

5. Number of dragonfly and alderfly families.

This metric is the sum of the number of dragonfly (Odonata) and alderfly (Megaloptera) families.

6. Number of beetle families

This metric is the sum of the number of beetle (Coleoptera) families present at the site. The metric has a relationship with bank quality as well as water quality.

Results

The pond was surveyed using the PSYM methodology enabling an assessment of its biological quality to be made together with a comparison with other ponds in the area.

The PSYM scores are placed in four categories which reflect the ecological quality of the pond:

0-25% is very poor, 26-50% is poor, 51-75% is fair, and 76-100% is good

Royal Derby Hospital Balancing Pond

Site and sample details

Grid reference: SK 32440 35570

Site Name: Royal Derby Hospital Balancing Pond

Location: West of former Kingsway Hospital, Derby

Owner/site access details: Royal Derby Hospital

Survey Date: 5th August 2011Surveyors: Trevor Taylor (Derbyshire Wildlife Trust)

Environmental Data

Altitude: (m)74m aslpH:7.80
Shade: % pond overhung:1%% emergent plant cover15%
Inflow (absent = 0, present = 1):1Pond area (m2)2,501m2
% of pond margin grazed:0

Pond base: categories into one of three groups; 1=0%-32%, 2=33%-66%, 3=67%-100%

Clay/silt:1Sand, gravel, cobbles:3Bed rock:1
Peat1Other1

Emergent plants Rarity Score Trophic Ranking Score
 
Epilobium hirsutum, Great Willowherb1-
Filipendula ulmaria, Meadowsweet 1 -
Iris pseudoacorus, Yellow Iris 1 -
Juncus articulatus, Jointed Rush 1 -
Juncus effusus, Soft Rush 1 -
Juncus inflexus, Hard Rush1-
Typha latifolia, Bulrush18.5
 
Submerged plants
 
Potamogeton pusillus, Lesser Pondweed29
Zannichellia palustris, Horned Pondweed210

Number of emergent and submerged species - 9
Number of uncommon species (with a rarity score of 2 or more) - 2

Trophic Ranking Score - 9.17

Macroinvertebrates
Group 2 taxa (BMWP:8)
Aeshnidae (Dragonfly, Brown Hawker, (Aeshna grandis))
Libellulidae (Dragonfly, Broad-bodied Chaser (Libellula depressa))

Group 3 taxa (BMWP:7)
Caenidae - Mayfly

Group 4 taxa (BMWP:6)
Gammaridae - Crustacean (Shrimp)
Coenagriidae - Damselfly

Group 5 taxa (BMWP:5)
Gerridae - Water bug (Water skater)
Pleidae - Water bug
Corixidae - Water bug (Water boatman)
Group 6 taxa (BMWP:4)
Sialidae - Alderfly
Baetidae - Mayfly

Group 7 taxa (BMWP:3)
Lymnaeidae - Snail
Sphaeridea - Pea Mussel
Glossiphonidae - Leech
Asellidae - Crustacean (Water slater)

Group 8 taxa (BMWP:2)
Chironomidae - Fly (Non biting midge)

Group 9 taxa (BMWP:1)
Oligochaetae - True Worm

Total No. Of taxa16
Total BMWP Score73
ASPT4.6
No. OM taxa4
No. Coleopt taxa0

Index of Biotic Integrity (PSYM Score %) = 56. As such the pond would be considered to be in fair ecological condition.

This represents a slight decrease in the ecological condition of the pond since 2005 when a survey undertaken as part of the Derby City Pond Survey returned a PSYM score of 61%. This slight decrease would appear to be the result of an apparent decline in the presence of Coleoptera (water beetles). No beetles were recorded during the 2011 survey.

A conductivity test to measure of the total quantity of chemicals dissolved in the water returned a reading of 1350µS/cm. This figure indicates that the pond is somewhat contaminated presumably as a result of run-off from the car park areas. Where conductivity is 500-1000 + µS/cm this is usually a sign of some kind of pollution and a perfectly clean water pond would have a figure of 100µS/cm or less.

Survey Results

Broard Bodied Chaser

Whilst the pond shows a slight decline in overall ecological quality in recent years, it still supports a good range of aquatic macroinvertebrates, particularly dragonflies with Broad-bodied Chaser exhibiting mating behaviour and ovipositing during the survey visit as well as the presence of larvae.


Right: Broard Bodied Chaser

Also, of particular note is the presence of the submerged aquatic plant Zannichellia palustris, Horned Pondweed, in the margin of the eastern bank of the pond. The plant is a Derbyshire Red Data Book species which is considered to be locally declining.

Presumably due to its relatively undisturbed nature, the pond attracts a reasonable amount of bird activity with Coot, Moorhen, Mallard and Little Grebe nesting at the site and Reed Bunting present in the surrounding willow and bramble scrub.

It is somewhat disappointing and surprising that the pond does not support any amphibian interest. Torchlight and bottle trapping surveys undertaken on 21st April 2004, April 8th 2011 and March 23rd 2012 all failed to find any evidence of amphibians.

The pond and surrounding habitats provide excellent foraging opportunities for bats.

Management History

It is understood that some initial planting was carried out when the pond was created but has since been left to colonise naturally. There is little evidence of management with the exception of some Typha removal in the vicinity of the outfall, presumably to maintain functionality.

Photographs would seem to indicate that the pond has been enlarged in the intervening period between the pond survey carried out in 2004/5 as part of the Derby Coty Pond Survey and the current surveys undertaken in 2011/12. The earlier surveys identified a band of Typha around the margins of the pond while the recent surveys show a band of Typha running through the centre of the pond.

Derby Royal Hospital

August 2005

Derby Royal Hospital

August 2011

Management Recommendations




Derby Royal Hospital Map