The Forest Town Nature Conservation Group (FTNCG) monitors the water quality at both the ponds at Spa Ponds and at the River Maun on Packman’s Bridge, and from time to time also get water quality monitoring data from others such as the Environment Agency. We currently test the water around four times a year.
This work helps inform our management of the site – for example, we found out that the oxygen levels of the water coming from the spring was low, which inspired us to introduce a range of oxygenating plants, especially for Pond 1.
Water quality testing also helps us identify potential pollution or water quality incidents, whether that be from agricultural runoff into the ponds, or waste discharges into the river, etc.
FTNCG is part of FreshWaterWatch. We provide them with our ‘citizen science’ data, and they provide us with an affordable way to access testing equipment and associated chemicals.
The Forest Town Nature Conservation Group is a proud member of the Sherwood Catchment Partnership, which is hosted by the Nottinghamshire Wildlife Trust. The Sherwood Catchment Partnership is a subset of the River Idle Catchment Partnership. The Partnership is dedicated to conserving and enhancing the Rivers Idle, Ryton, Poulter, Meden, and – most importantly for FTNCG – the River Maun, their tributaries and surrounding land, to create a healthy and wildlife rich water environment for the benefit of both people and biodiversity. You can read more about the work of the Partnership at: https://catchmentbasedapproach.org/get-involved/idle/
Our monitoring data for Spa Ponds and the River Maun
Notes on where we take the readings:
- Pond 1 is the southernmost pond (farthest from the River Maun) and Pond 4 is the northernmost pond (closest to the River Maun).
- All pond measurements taken from western side of pond but well away from river bank.
- Pond 1 measurement is taken from next to the spring.
- River Maun measurements are taken near to Packman’s Bridge
Presentations on Spa Ponds water quality
Spa Ponds monitoring – Findings and interpretation
We have adapted some of the explanations from the January 2023 presentation on Spa Ponds Water Quality Interpretation and added in our additional understanding. Be aware that there may well be other valid interpretations of the same data, and some of the information provided is just a summary.
The graphs shown are from FTNCG’s 2016-2019 monitoring and most were produced for a presentation Phil gave in 2019 and also fed into 2023 presentation. We changed our monitoring approach slightly from 2019, but the historic results remain indicative of Spa Ponds water quality results.
Temperature
Background:
Changes in temperature influence water chemistry (e.g. oxygen dissolves more easily in cold water) and living things (e.g. fish are more active in warmer water).
Spa Ponds:
Average temperature across the ponds from 2016-2019 was around 9.7 degrees Celsius, ranging from around 3 to around 19. The River Maun’s temperature was 12, ranging from 7 to 18.
We tend to find that the temperature of the ponds reflects the air temperature but is less volatile, avoiding its peaks and troughs. The River Maun is much more consistent in its temperature and less impacted by the air temperature.
Temperature in the ponds can be affected by tree cover, which is itself impacted by the season and by efforts to remove selective trees around the ponds to let in more light and create more disruption to the surface of the water to discourage eutrophication.
Ammonia
Background:
Ammonia can be created by the decay and breakdown of organic material, e.g. leaf litter as well as sewage effluent / agricultural (fertiliser) run off and industrial process products (cleaning agents).
Ammonia exists in two forms: ammonium (NH4+) and unionised ammonia (NH3) – proportions of each depend on pH and temperature. NH3 is toxic to fish and invertebrates.
Toxicity increases as pH and temperature increases. (2 mg/l and 0.02 mg/l).
Spa Ponds:
Spa Ponds levels measured in 2016-2019 were within the Water Framework Directive range for High or Good classification.
We find ammonia significantly lower in Pond 1 the other ponds. This could relate to Pond 1 containing our main spring as well as the fact that we measure from just next to the spring. The ammonia levels at other ponds are reasonably stable. Pond 2 is sometimes higher, which could be due to leaf litter and/or agricultural runoff.
The spike shown in the above graph is for River Maun, and was taken on a rainy day, and could potentially be related to upstream catchment and / or sewage inputs.
pH
Background:
pH is a measure of how much like vinegar (acidic) or bleach (basic) the water is. A pH of 7 is considered neutral.
Scale = 1 (acidic) – 14 (basic). A small change in pH can be significant because it is measured using a log scale – pH 5 is 10x more basic than pH 4.
For High / Good Water Framework Directive classification (rivers) pH should be between 6 and 9.
Extreme changes in pH can be directly toxic whilst small changes can alter the toxicity of other chemicals and affect living things (e.g. cause irritation to fish gills).
Spa Ponds:
The ponds (and the River Maun) in 2016-2019 had an average pH level of 7.5 with a typical range of 7.0 to 8.0 but Pond 2 was once measured at 9.0. This indicates that pH levels have been consistently High / Good when measured.
Phosphates and nitrates
Background:
Phosphates and nitrates are naturally occurring substances which are important in biological processes. However, they can also come from sewage effluent (washing detergent) and agricultural (fertiliser) run off.
Excessive nutrient load contributes to eutrophication – rapid plant / algae growth which causes reduction in dissolved oxygen and light levels, causing stress on aquatic organisms.
If phosphates are higher when it is wet, this could indicate runoff, and if it is higher when it is dry then this could indicate point source pollution or other biological processes.
Spa Ponds:
FreshWaterWatch reports that at times the recorded nutrient levels at Spa Ponds could “favour the formation of algal mats which may influence aquatic biodiversity”. This indicates that measures to improve water quality at Spa Ponds could enhance biodiversity.
Phosphates
Results from phosphate testing (mg/L). Last graphic is FreshWaterWatch chart for ponds 1-4 (2019-2024)
Spa Ponds:
Based on monitoring November 2016 to February 2019 monitoring, we have mean average for the ponds and the river. Pond 1: Mean of 0.25 (range of 0.04-0.37), Pond 2: Mean average of 0.54 (range: 0.13-1.7), Pond 3: Mean 0.36 (range: 0.09-1.12); River Maun mean of 1.26 (Range: 0.58-1.97).
The lower levels in Pond 1 could relate to the presence of the spring and the fact that measurements are taken near the spring. Levels are higher in Pond 2 which could relate to more input sources or leaf breakdown. It then goes down for subsequent ponds, indicating the phosphates are either being used up or locked up by biological processes. This means that by the time the water from Spa Ponds reaches the River Maun, it is lower in phosphates than the river.
Nitrates
Results from Nitrate sampling (ppm)
Spa Ponds:
Nitrates are consistently higher in Pond 1, which is likely to relate to the spring and the fact that measures are taken next to the spring. As the nitrates are used or locked up by biological processes, the levels go down in other ponds which mean that by the time the water feeds into River Maun the nitrate levels tend to be far lower than the level in the river. High levels in River Maun could relate to point source emissions and diffuse runoff.
Turbidity
Background:
Turbidity measures water clarity, with a higher value indicating more cloudy water. Generally speaking, the higher turbidity implies poorer the water quality. Sources of turbidity include run-off (from diffuse or point sources), erosion, biological activity (such as fish disturbing the sediment) and high organic or sediment content in a pond. Rain can increase runoff, as can increased biological activity (fish movement / algal blooms – higher in warm weather).
According to DataStream: “High turbidity can have negative impacts on fish and other aquatic life. Algae and other aquatic plants need light to grow and high turbidity will decrease underwater light availability and If there is a lot of floating algae in a lake, this can block out light that other plants need to grow. High turbidity due to algae can also affect fish because when large amounts of algae die, oxygen is used up to decompose them, leaving less oxygen for the fish.”
One way to measure turbidity is Nephelometric Turbidity unit (NTU). For drinking water, the NTU should the World Health Organisation says that the water should have an NTU of less than 1 and the aim should be to keep it below 5.
According to DataStream: “Turbidity can vary widely between each river and lake, and also over time. For this reason, most government guidelines provide a maximum allowed increase from normal background levels for each water body. Turbidity values less than 10 NTU are considered low, a value of 50 NTU would be considered moderately turbid, and very high turbidity values can be more than 100 NTU.”
Spa Ponds:
Generally speaking the turbidity at the ponds between 2016 and 2024 is low, which is a good sign.
There was a specific incident in June 2017 on a rainy day where turbidity was markedly higher at the ponds and we believe this was most likely due to rain as the conditions were rainy and the levels at the River Maun was also higher.
In March 2019 FTNCG moved from % turbidity to an NTU model. From 2019 onwards, turbidity is generally found as “<14” NTU which is the lowest level on our tests, but on the 20th of March 2019 Pond 2 was found to have a NTU of 19-25 – no specified cause for this elevation was found, but the levels at the other ponds were <14 so it does not seem to have notably affected the wider site.