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Nitrate Vulnerable Zone (NVZ) designation, 2017 Eutrophication (lakes) Publication Date: June 2016 Page 1 of 14 NVZ Name: Crose Mere NVZ ID: EL121
Nitrate Vulnerable Zone (NVZ)
designation, 2017 Eutrophication (lakes)
Publication Date: June 2016
Page 1 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Evidence of eutrophication 2017
This document provides a summary of the evidence used in proposing an area of land as one which should be, or should continue to be, designated as a Nitrate Vulnerable Zone (NVZ) for the purposes of the Nitrate Pollution Prevention Regulations 2015. A full description of the methods used in developing the NVZ proposals is set out in the detailed methodology for eutrophication-related NVZs, available via http://apps.environment-agency.gov.uk/wiyby/141443.aspx . These methods were developed under the guidance of a review group convened by the Defra for the last NVZ review (2011-2013), which included representatives from the farming and water industries as well as independent academic experts. Minor refinements to the methods have been made for the current review. NVZs are areas of land that drain to polluted waters and which contribute to the pollution of those waters. Polluted waters include those which are eutrophic or may in the near future become so if the Regulations were not to apply there. Eutrophication is defined as “the enrichment of water by nitrogen compounds, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned”. For both freshwaters and saline waters, a weight-of-evidence based approach to assessing the risks and impacts of eutrophication was employed. The evidence for individual water bodies was assessed against a national suite of criteria for eutrophication in the different categories/ types of water for review. The criteria are both quantitative and qualitative and reflect scientific understanding of the process and effects of eutrophication. They are broken down in the same way for each water category as follows:-
Nutrients
Plants/algae
Secondary and other effects For each designated or candidate water body which might meet the criteria for eutrophication, a datasheet such as this one was completed, bringing together information about the water body, its catchment, its uses, evidence of eutrophication and the sources of nitrogen input. This document is a record of the evidence used in the designation process, including results from national monitoring and assessment programmes, and further information supplied by Area staff. The proposals for NVZ designation are made as a result of close working between Area and national Environment Agency teams, with further quality assurance for the eutrophication designations through the use of a national expert panel. An accompanying guide to these datasheets is available, which provides an explanation of the contents, acronyms and technical terms.
Some features of the maps within this report are based on digital spatial data licensed from the Centre for Ecology and Hydrology, ©. Please note that any maps shown here have not used detailed field boundaries and therefore represent the indicative 'soft' boundary only. The definitive NVZ area can be seen on the “What’s in Your Backyard” (WIYBY) website ((http://apps.environment-agency.gov.uk/wiyby/141443.aspx).
Page 2 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
35211WB ID: 2013 NVZ status: Designate (precautionary)
Section 1. Lake and catchment characteristics
Shropshire Herefordshire Worcestershire and
Gloucestershire
343068
15.2
No
High alkalinity,shallow,small,lowland
EA Area
Lake grid co-ordinates (Easting/Northing)
Lake waterbody area (ha)
Is the lake heavily modified according to WFD?
WFD Lake Typology
Lake attributes
330513/
Lake Alkalinity (ueq/L) 3139
Mean lake depth (m) 3.7
Does stratification occur? Stratification likely most years
NoIs this waterbody a reservoir?
Natural or artificial lake:
Natural --- The majority of the Shropshire and Cheshire meres developed in natural depressions in the
glacial drift.
Type of artificial lake:
n/a
Lake perimeter (% artificial)
Natural
Significant changes in lake level due to seasonal drawdown:
N
Pumped storage or other reservoir:
n/a
Information on abstraction (if available)
Page 3 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Lake catchment attributes191Lake catchment area (ha)
If pumped, pumped catchment area (ha)
Primarily groundwater
Hydrological character
Comments on accuracy of lake catchment:
Is the map representative of the natural catchment?
Yes --- Map looks reasonable based on surface water catchments and topography.
Is the map representative of the artficial catchment?
n/a
Please note that the map above has not used the detailed field boundaries and is the indicative 'soft' boundary.
The definitive NVZ area can be seen on the Environment Agency website (www.environment-agency.gov.uk)
Page 4 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Section II - Waterbody uses
Controlled water (Section 104 of Water Resources Act):
No
Public Water Supply:
No
Drinking Water Protected Area:
No
UWWTD designation
No
Used for hydropower or flow regulation:
n/a
Accessiblity to public:
Not easily accessible, few visits --- Not directly accessible by car, one footpath passes nearby.
Recreational fishing:
Moderate benefit --- Fishing takes place with stocking in 2008.
Contact watersports
No activity
Nature of watersports (if applicable):
---
Other public benefit visits:
Little activity
Conservation value of lake:
National
Habitats Directive site:
Not SPA or SAC --- Ramsar, SSSI
SPA or SAC for aquatic interest features
---
SSSI or local conservation designation:
SSSI
Description of Aquatic interest features:
--- Bog mosses Sphagnum spp. reedmace Typha angustifolia but also comprising an area of common reed Phragmites
australis.
Water Supply:
Recreational use:
Conservation status:
Page 5 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
0.5
60
Not confident
Not confident
2010 - 2014
75th percentile annual TON (mg/l)
Total number of TON samples
Confidence of annual 75th %ile TON exceeding 1 mg/l
Confidence of annual 75th %ile TON exceeding 2 mg/l
Date range of TON samples
Total oxidised nitrogen (TON) data
TON monitoring data
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
04/02/2010
04/05/2010
04/08/2010
04/11/2010
04/02/2011
04/05/2011
04/08/2011
04/11/2011
04/02/2012
04/05/2012
04/08/2012
04/11/2012
04/02/2013
04/05/2013
04/08/2013
04/11/2013
04/02/2014
04/05/2014
04/08/2014
04/11/2014
sample date
TO
N m
g/l
27942900
0.2
30
Mean summer TON (mg/l)
Total number of summer TON samples
Section III - Causes - Nutrients
Page 6 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
1.4
60
High
Not confident
2010 - 2014
Mean annual TN (mg/l)
Total number of TN samples
Confidence of annual mean TN exceeding 1 mg/l
Confidence of annual mean TN exceeding 2 mg/l
Date range of TN samples
Total nitrogen (TN) data
TN monitoring data
0
0.5
1
1.5
2
2.5
3
04/02/2010
04/05/2010
04/08/2010
04/11/2010
04/02/2011
04/05/2011
04/08/2011
04/11/2011
04/02/2012
04/05/2012
04/08/2012
04/11/2012
04/02/2013
04/05/2013
04/08/2013
04/11/2013
04/02/2014
04/05/2014
04/08/2014
04/11/2014
sample date
TN
mg
/l
27942900
Does any other(e.g. EA non-WFD, or third party) monitoring data for the lake
provide improved evidence of significantly elevated nutrient nitrogen?
Page 7 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
66
Moderate
100%
2010 - 2014
Annual geometric mean TP (ug/l)
WFD face value TP class
Confidence of moderate or worse TP status
Date range of TP samples
Total phosphorus (TP) data
TP monitoring data
0
100
200
300
400
500
600
700
04/02/2010
04/05/2010
04/08/2010
04/11/2010
04/02/2011
04/05/2011
04/08/2011
04/11/2011
04/02/2012
04/05/2012
04/08/2012
04/11/2012
04/02/2013
04/05/2013
04/08/2013
04/11/2013
04/02/2014
04/05/2014
04/08/2014
04/11/2014
sample date
TP
ug
/l
27942900
Does any other(e.g. EA non-WFD, or third party) monitoring data for the lake
provide improved evidence of significantly elevated nutrient phosphorus?
--- Unsure on what data Natural England has collected.
Page 8 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
7488
7144
8
7496
From all agricultural sources
From agricultural sources minus atmospheric deposition
From urban sources
From all sources
From all sources (minus atmospheric deposition)
Nitrogen loading estimates based on catchment map area
14.5
0
14.6
Leached N
(kgN/yr)Conc. (mg/l)
14.1
7152 13.9
Nutrient sources
Significance of loading from agricultural sources to the catchment of the lake
Principal source --- There has been source apportionment works completed using LESA -NP v3 model
for the majority of the Shropshire Meres. This model shows the principal source is agricultural (mainly
arable)
Significance of loading from human habitation to the catchment of the lake
Minor source --- Very unlikely as very rural catchment.
Significance of any other sources of nutrient loading to the lake or its catchment
Local assessment 2015
104Ranking based on nitrogen loading from agricultural sources
NEAP - N assessment 2014
Page 9 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Section IV - Response - Plants/Algae
23
Moderate
100%
10
Annual mean Chlorophyll (ug/l)
WFD face value Chlorophyll class
Confidence of moderate or worse status
Chlorophyll Good/Moderate boundary value
total number of Chlorophyll samples
Chlorophyll data
Chlorophyll monitoring data
0
20
40
60
80
100
120
140
160
180
04/02/2010
04/05/2010
04/08/2010
04/11/2010
04/02/2011
04/05/2011
04/08/2011
04/11/2011
04/02/2012
04/05/2012
04/08/2012
04/11/2012
04/02/2013
04/05/2013
04/08/2013
04/11/2013
04/02/2014
04/05/2014
04/08/2014
04/11/2014
sample date
Ch
loro
ph
yll u
g/l
27942900
59
2010-2014Date range of Chlorophyll samples
Page 10 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
0.17
Poor
100%
2011 - 2013
EQR
WFD face value class
Confidence of moderate or worse
status
Date range of samples
Total number of samples/surveys
Phytoplankton
(Pluto EQR)
Macrophytes
(EQR)
Diatoms
(EQR)
0.4
Poor
100%
2009 - 2012
0.5
Moderate
100%
2011 - 2013
2 4
Palaeolimnology
1.28Change as Square Chord Distance
Change in Diatom community Significant Change
0Number of years when algal blooms were observed based on
reactive monitoring 2010-2015:
Does any other (e.g. EA non - WFD, or third party monitoring data for the lake
provide improved evidence of eutrophication? (local judgement)
Strengthens evidence --- All evidence we currently have gives high confidence in the fact that this waterbody is
suffering from eutrophication. On CPS the cycle 2 classification for this waterbody for 2015 is Poor. Macrophytes
and phytobenthos and phytoplankton are the biological quality indices that are causing this failure.
To which biological element(s) does it relate?
More than one (describe) ---
Evidence that designated aquatic interest features associated with the lake show
evidence of eutrophic disturbance? (local judgement)
Likely to be affected- SSSI citation states 'Crose Mere is an eutrophic mere with narrow marginal zones of reed
swamp and fen'.It is likely that the high winter nitrate values are impacting the aquatic macrophytes. Evidence for
eutrophication is strong. Historical evidence of eutrophication in this mere back to 1750. The data for Crose Mere,
however, showed strong seasonal trends in both orthophosphate and nitrogen both of which peak during the winter
months a trend which has been attributed to external nutrient loading (Atkins, 2012). This is supported by the work
of Fisher (2003) who examined sediment cores from 14 of the Shropshire and Cheshire Meres and concluded that
the sources of both TP and TN within the surface water of Crose Mere were external and not through internal
loading. More recent source apportionment work has been carried out using the LESA-NP V3 model, where arable
farming was identified as being the primary source of both phosphorous and nitrogen. Lakes with eutrophication
weight of evidence database shows a high confidence that Crose Mere is suffering from eutrophication.
Strength of evidence (local judgement)
Strong evidence ---
Local judgement on the evidence of eutrophic disturbance
Y, definitely --- There is evidence these meres have been eutrophic for over 100 years and with extra inputs from
agriculture within the catchment we are confident in classing this waterbody eutrophic
33
Other responses
Page 11 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Review of evidence and recommendations
Existing designation - check needed
Current assessment of weight of evidence supporting
designation in 2017
Comments and decisions
WFD Weight of evidence for eutrophication:
WFD overall ecological status : Poor
Confidence in WFD status : Very Certain
Existing designation - N remains >1 mg/l and there is evidence of ecological impact for eutrophication.
Recommend continued designation.
Agreed with provisional decision to continue designation
Recommended action :
First national panel
Comments from second national panel :
Comments from first panel:
Second national panel
Local summary and recommendation:
This is an existing NVZ - based on the strength of evidence - elevated N, failing of P and ecological
evidence of impact, the local EA team recommends continued designation.
Certainty of eutrophication problem based on core WFD tools: Very certain
eutrophication problem
Certainty of eutrophication problem based on overall weight of
evidence:
Very certain
eutrophication problem
Recommendation: Continued designation
Page 12 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Final summary (2017)
2008 Decision: Not designated
2013 Decision: Designate (precautionary)
Lake Description:
Crose Mere is a naturally nutrient rich, high alkalinity, shallow, Mere. The majority of the Shropshire and
Cheshire meres developed in natural depressions in the glacial drift. SSSI citation states "Crose Mere is an
eutrophic mere with narrow marginal zones of reed swamp and fen". It is also a RAMSAR site.
Why the lake should be designated as a Polluted Water (eutrophic):
Crose Mere is an existing eutrophic waters NVZ designation, it also lies within a surface water NVZ. While
there was a slight decrease in mean TON concentrations since the last review, the increased winter peaks in
recent years are a cause for concern. The ecology continues to show eutrophic impact. Continued designation is
therefore proposed.
Phosphorus:
The WFD classification for total phosphorus is Poor status.
Nitrogen:
While 75th percentile TON decreased from 0.7 to 0.5 mg/l compared to the previous review, the mean annual TN
has stayed the same at 1.4mg/l. Since 2013 there have been greater fluctuations in concentration of TN and TON,
winter peaks being higher than those in the preceding years.
Supplementary evidence:
Source apportionment work has identified arable farming as the primary source of nitrogen and phosphorus for
this lake.
Ecological response:
Both phytoplankton and macrophytes are at Poor WFD status, while chlorophyll and diatoms are at Moderate
status, indicating eutrophic impact.on the ecology. There is evidence of nitrogen limitation occurring during the
growth season.
2017 Recommendation: Continued designation
Page 13 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
Page 14 of 14
NVZ Name: Crose Mere
NVZ ID: EL121
