Working with water
How The Watercress Company works with 50 million litres of
water per day and achieves the targets set by the EA
Watercress is a truly unique crop and the vital ingredient for growing watercress is, of course, water – pure, mineral-rich spring water, from which this peppery leaf derives its powerhouse of nutrients.
This water originates from deep aquifers below ground and flows through our beds before being returned to the river system. It is our aim to grow watercress with as little effect on water quality as possible.
Each farm has its own abstraction licence and discharge permit, issued and
The two main considerations in our discharge waters are suspended solids (from bed cleaning) and phosphate (from fertiliser applications).
Our farms in Hampshire discharge through settlement ponds into the River Itchen, a chalk river which has been designated as a Special Area of Conservation (SAC) under the EU Habitats Directive. This designation means that the targets for water quality are much more stringent than the Water Framework Directive targets which need to be met by watercress farms in other areas.
Because of this legislation, the Environment Agency (EA) has set limits for phosphate levels in watercress discharge water for any watercress growers discharging into an SAC. These limits were determined in 2014 and came into force in September 2016 and are very low, set typically at around 40 µg/l above base levels (base levels being the natural levels found in our spring water). As well as limits on phosphate, a limit was also set for ammoniacal nitrogen at 0.5mg/l which came into force immediately when the permits were first issued in 2014.
How do we reduce fertiliser use, manage
effluent and reduce suspended solids ....…
Suspended solids are created when we clean out a watercress bed. This clean out process is necessary before the beds can be re-drilled with a new crop. In order to reduce the level of suspended solids generated from this operation the water is sent through settlement ponds. These ponds are designed to slow the water flow down so that the solids are able to settle out before reaching the discharge point. The ponds are cleaned out on average once per year to allow their efficient operation. Since 2017 we have reduced the number of times each bed is cleaned out and replanted thereby vastly reducing the amount of suspended solids produced. Our aim for 2018 was to drill only twice in each bed and this has reduced the loading on the ponds and helped to protect the downstream environment.
The by-product of the cleaning out process is a mix of watercress waste and gravel. We have recently redeveloped our composting area for this material. Once it has been removed from the bed the material is initially stored on a concrete pad. The liquid effluent from the watercress is collected into a tank and this liquid is then used as an additional nutrient source.
We have been able to reduce our fertiliser requirement by reducing our plant densities at the time of sowing. This lower density enables the growing plants to take up a greater percentage of the available nutrition. It is worth noting that, for the majority of the year, we use no fertiliser at all and, during the summer growing period, fertiliser is only needed for less than 4% of the plant’s growing life. As the permit limits set by the EA for both phosphate and ammoniacal nitrogen are so low, we have had to trial innovative methods to reduce the quantity and type of fertiliser in order to successfully meet the new limits.
Whilst we were able to remove nitrogen applications completely, phosphate has proved more challenging and complicated. Phosphate deficiency can lead to an unmarketable crop, particularly during the flowering period. Between 2007 and 2017 we have managed to reduce the quantity of phosphate being used on our farms by 87.5%, however this has not been achieved easily and has come at considerable cost in terms of productivity. Additionally we are seeing elevated levels of flowers and purple stems which devalue the finished product however this huge reduction in applications has seen us achieve the standard set by the EA in the first year. Our compliance results are based on samples taken by the EA and these results are below.
How we monitor ourselves with testing of
water and calculating annualised averages
In addition to the EA monitoring of our discharges, we also deploy our own autosamplers (ISCO 3700s) on each farm and monitor phosphate discharges for the 24 hour period after a fertiliser application has taken place. We combine the information from this testing with information from the periods when we do not apply fertiliser to calculate an annualised average. This testing is significantly more frequent than the tests carried out by the EA and corroborates their findings. We know that there are still peaks in the levels of phosphate after a fertiliser application, but these peaks are short lived and when averaged out, the discharge levels are below permit levels. In fact there is evidence that, in winter, watercress actually removes a certain amount of phosphate from the incoming water (although this reduction is not used in the calculations)
In 2018, we carried out some intensive monitoring on the discharge from one of our farms and at two further sites; one 1km downstream and another 3.3km downstream. We timed this testing to ensure that we were testing after multiple fertiliser applications. Although there were some peaks at our precise discharge point, no effect was measured at either the 1km or 3.3km testing points downstream. Based on the levels taken from our discharge (without even adding in the period of the year when we don’t apply any additional nutrients) the average level detected was well below the level required by our permit.
In 2016, we asked an independent freshwater ecologist (Aquilina Environmental) to carry out an invertebrate survey at one of our discharge points.
Following the standard EA sampling protocol, aquatic macroinvertebrates were collected using a standard size FBA D-frame pond net from the major habitats along the stream (stands of different wetland plants, distinctive substrates, tree roots etc.). All the different habitats present were allocated a proportion of the overall sampling time (3 minutes) and different areas of the same mesohabitat were subsampled to ensure that as great a range as possible was sampled.
Each location was also searched for an additional minute looking for surface dwelling animals such as water skaters and whirligig beetles and inspecting submerged habitats such as logs and larger stones for attached animals.
We imagined that the results from our discharge points would be broadly similar, as the water quality is the same at each farm, however each of the surveys gave quite different results. This was because each of the discharge points had different habitats with varying levels of shading and water flow. The substrate also influenced the findings as in some locations there were gravel bases and others had a silty substrate. It was evident that these environmental characteristics have a very significant effect on biodiversity when water quality is the same.
We have repeated that survey again this year with an addition of a further two testing locations. We have seen an improvement in biodiversity over the two years and the report presenting this information in detail can be found below.
This type of survey work will be carried out on a regular basis now that we have established some baseline levels, and any improvements can be recorded.
We have also carried out a survey on one of our farms upstream of any settlement facilities where the only water was that which has come from watercress beds. The aim of this study was to see which species were living in watercress discharge water without any outside influences, and to investigate what could be done to improve this biodiversity which will be monitored by further survey work in the future. A video of this survey work, with explanations from Robert Aquilina will be uploaded soon so keep your eyes peeled.
The results of this survey work are published below.
Why we are under pressure and what we have
done to try and engage with local groups
There has been significant pressure from the fishing community and local environmental groups, both on the watercress industry to reduce the levels of phosphate in the discharge water, and on the EA to regulate effectively.
We have met with Salmon and Trout Conservation UK and with local landowners to tell them what we have been doing to reduce our discharge levels.
We also have representatives who attend meetings of the Upper Itchen Initiative, a group that has been meeting for 10 years, concerned with the protection of the Upper Itchen river catchment and its tributaries. The group comprises of statutory bodies, riparian landowners, business interests and local stakeholders. This group is kept informed on our progress at each meeting.
We also attend meetings of the Test and Itchen Catchment Partnership which brings together local people and organisations to plan and deliver positive actions that will improve our water environment and are a supporter of their lottery funded Watercress and Winterbournes project.
Over the past few years we have been working closely with the EA to formulate an action plan and to report to them on our progress. This successful working relationship has contributed to the success we have had with permit compliance in the first year of monitoring.
Macroinvertebrate Survey of Manor Farm outflow, Old Alresford , Hants
Report prepared by Robert Aquilina MSc MCIEEM
Macroinvertebrate Survey of three watercress farm outflows, Alresford , Hants
Report prepared by Robert Aquilina MSc MCIEEM
Macroinvertebrate survey of Drayton watercress farm outflow, Alresford, Hants
Report prepared by Robert Aquilina MSc MCIEEM
Watercress farming, A new era - by Ollie Bedford