Hydrology Assessment June 2017
Lower Test Project:
Hydrology assessment of Proposed Licence Changes to Testwood PWS and Lower Test Flow splits sensitivity analysis
June 2017 Hydrology Assessment June 2017
Contents 1. Background ...... 3 2. Aim of Report ...... 4 3. River Test Catchment Description ...... 4 4. Resource Assessment ...... 6 4.1 Environmental Targets ...... 7 4.1.1 EFI ...... 7 4.1.2 Salmon migration protection flow requirements criteria ...... 8 4.1.3 River Test and Lower Test Valley SSSIs and Solent & Southampton Water Ramsar habitats and species Criteria ...... 8 4.2 Flow Data ...... 9 4.2.1 Gauged Data ...... 9 4.2.2 Natural Data ...... 12 4.3 Artificial Influences ...... 15 4.4 Additional Assessment Points in Ledger ...... 17 5. Current Lower Test WR Assessment ...... 17 6. Licence Change Options ...... 20 6.1 Option 1: Change licence conditions to meet EFI ...... 21 6.2 Option 2: Change licence to Average Recent Actual Quantities ...... 23 6.3 Option 3: Change current HoF to the in-river salmon migration protection and salmon entry protection HoFs ...... 23 6.4 Option 4: Change current HoF to the in-river salmon migration protection and salmon entry protection HoFs along with a reduction in licence quantities to meet EFI ...... 24 6.5 Option 5: Change licence to Voluntary Licence conditions ...... 26 6.5 Option 6: Alternative Management – Flow Splits ...... 28 6.5.1 Methodology: Reduce Broadlands Fish Farm Carrier flow by 60% ...... 28 6.5.2 Methodology: Coleridge Award Fixed flow split ...... 29 6.5.3 Reduce Broadlands Fish Farm Carrier Flow and use Coleridge Award Fixed flow split ...... 30 6.5.4 Alternative Management Option Results ...... 31 7. Change in Abstraction Sensitivity and EFI for the Test ...... 32 7.1 ASB3 High Sensitivity ...... 32 7.2 ASB13 Transitional waterbody ...... 33 8. Conclusions ...... 34 References ...... 35
Hydrology Assessment June 2017
1. Background To manage water effectively we need to understand how much is available and where it is available, after considering the needs of the environment. This is achieved by undertaking a resource assessment. Over many years we have assessed the impact of abstraction throughout the River Test. In 2000 we developed the Catchment Abstraction Management Strategies (CAMS) process as a consistent national tool for managing abstraction. The CAMS process was updated in 2013 to produce Abstraction Licensing Strategies (ALS) to help set out how we will manage the water resources of a catchment and contribute to implementing the Water Framework Directive (WFD).
The ALS process sets out a nationally consistent Resource Assessment Method (RAM). Water availability is determined by the relationship between each of the following main components of RAM:
a resource allocation for the environment defined as a proportion of natural flow, known as the Environmental Flow Indicator (EFI); the Fully Licensed (FL) scenario - the situation if all abstraction licences were being used to full capacity; the Recent Actual (RA) scenario – the amount of water which has actually been abstracted on average (usually over a set timeperiod).
The first Test & Itchen CAMS in 2006 (Environment Agency, 2006) indicated that at low flows the Lower Test catchment are “over-licensed”. This means that if existing licences were used to their full allocation they would have the potential to cause unacceptable environmental impact at low flows but that current actual abstraction is resulting in no water available at low flows. While the main aim of the abstraction management process is to set out how we deal with future abstraction it also identifies sites that are potentially being adversely affected by abstraction for inclusion in the Restoring Sustainable Abstraction (RSA) programme for investigation as funding and resources allow.
The 2006 CAMS and subsequent ALS identified concerns about the Testwood Public Water Supply (11/42/18.16/546) abstraction impact at fully licensed quantities on the River Test. Testwood is Southern Water’s largest single licence, located close to the tidal limit of the River Test. Testwood was therefore entered into the RSA programme and Southern Water began their National Environment Programme (NEP) for AMP 5 (2010 – 2015) to investigate Testwood’s impact on the Lower Test SSSI in 2011, after the precursor Environment Agency RSA project from 2009-2011. The Southern Water NEP concluded that there was minimal risk to the environment from both current and full use of the licence (Atkins, 2013).
Although we agreed that current abstraction levels do not appear to be having a significant impact on the River Test and Lower Test Valley SSSIs, we disagreed with Southern Water about the risk of potential impacts associated with increased abstraction levels. We believe that it is necessary to reduce the Testwood abstraction licence to prevent any risk of deterioration and to ensure protection of SSSI habitats and species and the downstream Ramsar site. Southern Water have indicated that they believe that the licence should be reduced but, due to the lack of information provided to show there is no risk of deterioration, there is no agreement with them about the changes needed.
Southern Water also contend that the Environment Flow Indicator and other target flow regimes should not apply in an environment affected by structures diverting flows and impounding rivers and so options of alternative river management could be considered to achieve the environmental objectives. No firm options have been proposed and so work is ongoing to change the Testwood licence to be a more sustainable abstraction.
Hydrology Assessment June 2017
2. Aim of Report This report has been produced to demonstrate current compliance conditions in the River Test and to test the environmental sustainability of options for changing the Testwood Public Water Supply Licence. The report will assess a set of proposed licence change options compared to the environmental outcomes measured by changes in flow set by the NEP project. This report does not discuss or validate the environmental outcomes.
Southern Water have been considering catchment management options including ways to modify the Lower Test flow splits to contribute the environmental objectives. No firm options alternative management option have been proposed. The secondary aim of this report is to complete a sensitivity analysis to assess whether there is any real benefit in managing the flow diversions to the environmental outcomes. It must be noted that the flow diversions in the Lower Test area are unlikely to have a significant effect on overall total flows entering the estuary, and all the diversions and offtakes are privately owned and are not currently subject to regulation and so the EA has no part in enforcing or managing the flow in those channels
3. River Test Catchment Description Detailed information on the catchment including the hydrology (river management, flow splits and diversions) of the lower River Test (from Timsbury to the estuary) was compiled by the Environment Agency as part of its Lower Test Project in 2009 and reported in the Baseline Data Report (Environmental Agency, 2010a) & Flow Diversion Scoping Report (Environment Agency, 2010b). A summary of this information is presented in this report.
The River Test is a naturally braided Chalk stream with high base flows of good quality water and designated SSSI. The Test rises on the Chalk at Ashe, near Overton and flows across the Chalk to the Chalk-Tertiary geology boundary at Timsbury. The Test gains water from the underlying Chalk and from several tributaries - the Bourne Rivulet, River Dever, River Anton, Pillhill Brook, Wallop Brook, and the River Dun. In most winters, the Somborne Stream also contributes flow.
Figure 3-1 Lower Test detailed Hydrology Hydrology Assessment June 2017
From Timsbury, the Test flows across the clays and sands of the Lower Test. The Tadburn Lake enters the main river in Romsey. It is a small tertiary stream with low summer flows and flashy winter flows. The River Blackwater, which rises from Chalk springs at Sherfield English, meets the river Test just downstream of Testwood before the river flows through the Lower Test Nature Reserve SSSI and discharging to Southampton Water at Redbridge. The Test at this point provide freshwater flows to the Solent Maritime SAC and the Solent & Southampton Water SPA and Ramsar conservation sites. The Lower Test SSSI is currently at favourable condition, while the River Test SSSI is at unfavourable condition.
Down to Timsbury the impact of abstraction and discharges on the River Test is balanced and so gauged flows are similar to natural. The most significant abstractions are from the Great Test. First the Nursling Fish Farm is licensed to abstract water, though this is now disused and is non-consumptive abstraction as it returns water to the Test, and then Southern Water abstract water at Testwood. The Testwood intake is located around 1,600m above the tidal limit shortly before the River Blackwater joins the River Test. There is no natural transition from river to estuary on the Great Test as there are significant structures located at Testwood Mill. The structures act to raise water levels in the river behind them, reduce velocity and prevent saline water from entering the lower reaches of the river. Without the structures, water levels would reduce, velocities increase and at times of high spring tides, saline water may reach further up the river network.
Throughout its length, the river Test flows in multiple braided channels. This is particularly pronounced in the Lower Test area where there are significant flow splits. Figure 3-1 shows the main flow splits in this area - Broadlands Fish Farm Carrier, Great-Lower Test split and Nursling Fish Farm diversion
The Broadlands Fish Farm Carrier, is an old water meadow carrier controlled by a sluice on the Broadlands Estate. The flow is lost from the River Test immediately upstream of the gauging station (GS) at Broadlands. In the past, average flows of around 80 Ml/d (0.93 m3/s) and low flows of around 45 Ml/d (0.52 m3/s) have flowed through this channel to join the River Blackwater and enter the River Test downstream of the abstraction intake. However, from May 2016 flows in this carrier have varied significantly due to a voluntary, experimental (time-limited) change in management of that channel by the Fishery, the aim of which was to restore greater flows to the main carrier for biodiversity purposes. Flows in the carrier are measured at M27 TV1 gauging station (SU3481016370) and also a monthly spot flow gauging site further upstream near Broadlands GS (SU3509117288).
Following a dispute between milling and angling interests, the flow split between the Great and Little Test was set by legally binding arbitration in 1931 (the Coleridge Award) which allowed one third of flow through the Little Test and two-thirds along the Great Test. Both branches of the river are now in single ownership so there is no further dispute and management is at the discretion of the owner and their tenants. The Environment Agency does not have a part to play in enforcing civil judgements. The flow split is controlled by Conagar Sluice and is reasonably stable, but under very low flow conditions, more than one third of the flow has been measured in the Little Test. Flows are measured at Conagar Bridge GS (SU3550915898).
Hydrology Assessment June 2017
Nursling Fish Farm abstraction licence (11/42/18.16/547). This fish farm carrier diverts water from the Great Test above Testwood (GS and abstraction) in to the Fish Farm and then can return water either directly downstream of the fish farm (SU or through Nursling Fish Farm Settling Ponds to downstream of the Testwood GS (SU3543015248) & abstraction, where the Blackwater confluences with the Test. In recent years the tendency has been to discharge directly from the FF, which is upstream of the Testwood abstraction and GS. This abstraction’s diversion has a potentially significant impact on the downstream river flows. The abstraction’s discharge also is part of the Testwood PWS abstraction MRF condition.
The Test Back Carrier is a small offtake from the Test just downstream of the Broadlands GS. The offtake and the carrier itself is not actively maintained currently and so there are periods when the carrier goes dry. The carrier re-joins the Little Test just downstream of Conagar Bridge. In the past, average flows of around 10 Ml/d (0.12 m3/s) and low flows of around 0 Ml/d (0.0 m3/s). The Test Carrier average flow is measured at SU3552815918 and is only 1% of the Test at Broadlands GS flow and so is not a significant diversion of water.
4. Resource Assessment
The resource assessment method for the ALS process is undertaken in the “Ledger” for a defined ALS catchment, in this case the Test & Itchen. The Ledger is an EA nationally consistent spreadsheet model tool. The Ledger RAM is undertaken an Assessment Point (AP) scale (e.g. for a catchment upstream of a Gauging Station) and a local water availability is calculated. The Ledger model was updated in 2008 to align its impact distributions and allocation modelling with the WFD which assesses Water Resources (WR) compliance on more detailed waterbody scale.
Ledgers are “live”, and are continuously updated with licence changes and/or data refinements from new conceptual understanding. Ledger data is fed into WFD modelling on a two year rolling programme and data is transferred twice a year. The data in the WFD modelling becomes a fixed data set and so may not match those in the current “live” ledger.
This report’s resource assessment is based on the updated 2017 Test & Itchen Ledger. This ledger differs from the previous 2013 Ledger as it includes updated flow data for the Lower Test APs to be consistent with an agreed data set, referred to a DG100, between the Environment Agency and Southern Water for the Lower Test (below Timsbury) in the NEP project. The data set used in the NEP investigations spanned 1996-2012 but has since been updated to 2015. The 2017 Ledger update also tries to match the DG100 agreed conceptual assumptions for the river network, e.g. what is classed as “natural” in the Lower Test system (see section 4.2.2).
This section 4 describes the data inputted into the 2017 Ledger and explains any significant differences in the data with the previously used 2013 Ledger and current WFD assessment.
Hydrology Assessment June 2017
4.1 Environmental Targets
4.1.1 EFI The ALS environmental target is the Environmental Flow Indicator (EFI). The EFI is based on the ecological sensitivity of a river to changes in flow, and has been set through expert opinion (WFD UKTAG, 2008) and at a level to support good ecological status. There are three “abstraction sensitivity bands” (ASBs) (Table 4.1-1) and each of these ands was developed from assessment of 3 components:
Physical typology – using river ‘types’. Macroinvertebrate typology – using expected Lotic index for Flow Evaluation (LIFE) scores Fish typology – using identification of a fish ‘guild’ expected under particular physical parameters.
Scores and confidence ratings from each component are combined to give the overall ASB for the waterbody. Each ASB has a different EFI associated with it allowing less abstraction in high sensitive sites and more in sites with lower sensitivity. The EFI resource allocation is defined as a proportion of natural flow and if flows fall below the EFI it is possible that there could be damage resulting from abstraction. The percentage deviation from natural flow allowed is defined for four flow conditions, ranging from naturally low (Q95) to naturally higher (Q30) flows (Table 4.1-1). The ASB for the main River Test channel and WFD WB GB107042016840 is classed as “2 - moderate sensitivity to changes in flows” and so its EFIs and allowable abstraction are defined as seen in Table 4.1-1. The River Test ASB is being investigated as it is suggests that some of the scores were too low and that the river has as high sensitivity (see section 9.1).
Table 4.1-1: Percentage allowable abstraction from natural flows at different abstraction sensitivity bands. Abstraction Sensitivity Q30 Q50 Q70 Q95 Band ASB3. 24% 20% 15% 10% high sensitivity ASB2. 26% 24% 20% 15% moderate sensitivity ASB1. 30% 26% 24% 20% low sensitivity
A deficit in relation to EFI indicates where abstraction pressure may start to cause an undesirable effect on river habitats and species. EFI only indicate where the environment might be being damaged from abstraction, ecological evidence must be linked to the deficit in flow to definitively know if the change in flow is having an impact. In this respect the ALS ledger is used as a tool to ensure future licences are environmentally sustainable, were there is no other local data to over-ride the EFI.
The EFI is also used in the hydrological classification for WFD to identify the water bodies where reduced river flows may be causing or contributing to a failure of good ecological status. This is called the compliance assessment. The EFI will be applied as a default flow target unless there is an agreed bespoke flow regime based on local evidence which supports GES and objectives given in the RBMP. In some cases, it may be appropriate to deviate from the EFI and require less restrictive or more restrictive alternatives based on local information.
It has also been argued throughout the NEP that the riverine EFI should not be applied to Lower Test APs since they are influenced by the tide and downstream structures. The ledger is a licensing tool and so it must keep the ASB2 EFI otherwise the Ledger would not apply enough environmental protection to any new or varied licence upstream. A sensitivity check of reducing the EFI to a transitional protection can be seen in section 9 for completeness. Hydrology Assessment June 2017
4.1.2 Salmon migration protection flow requirements criteria The focus of the potential licence change options is on reducing impacts on the salmon population. It is suggested that the imposition of a bespoke, evidence-based flow condition to protect salmon migration will provide much enhanced environmental protection leaving minimal risk to invertebrates, macrophytes and the habitats and species associated with the SSSI. In the Scoping Report for further work after the NEP we set environmental outcomes which a revised licence will have to meet:
1. A flow regime in the lower River Test that maintains or improves passage for migrating salmon, 2. A flow regime that maintains a water temperature profile in the lower River Test which is not raised as a result of increased abstraction, and is as resilient as possible to climate change, 3. The required effective screening of all abstraction intakes to prevent fish being drawn in and trapped at any stage of their life cycle 4. A flow regime that maintains or improves water quality in the River Test for salmonid populations
This report does not discuss the validity of the environmental outcomes or derivation of the salmon protection flows, these can be found in Fewings (2014), Environment Agency (2013b) and Environment Agency (2015). To assess whether a flow regime in the lower River Test attracts, maintains or improves passage for migrating salmon then abstraction scenarios must not cause flow to fall below:
390 Ml/d at the Test Total from March through December (to attract salmon into the River Test from the estuary) 265 Ml/d on the Great Test below the confluence with the River Blackwater (Testwood Bridge) from March through December (to maintain and protect salmon migration once in the River Test)
The 390 Ml/d at AP16 is the equivalent of 82% of QN99, and the 265 Ml/d is the equivalent of 85% of QN99 at Great Test AP.
These outcomes will be assess based on flow timeseries and EFI compliance as the ledger will not directly assess these flows.
To assess whether a flow regime maintains water temperature to support salmon spawning then it is suggested that a flow regime must meets EFI as that would mean it is supporting good with no risk of deterioration. The water quality outcome is liked to Dissolved Oxygen standards and it is suggest that based on compliance with the thermal environmental standards, if those outcomes are met then dissolved oxygen is unlikely to be elevated as a result of abstraction. The screening outcome is not measureable by flows and will be dealt with through fish screening regulations and licence conditions so this report will not assess any potential licence changes against this outcome.
4.1.3 River Test and Lower Test Valley SSSIs and Solent & Southampton Water Ramsar habitats and species Criteria Since the scoping report objectives were set, additional issues have been identified, including the need to ensure that there is no risk of deterioration under Water Framework Directive, and that impacts on the downstream Ramsar site are assessed and the site is Hydrology Assessment June 2017 protected. An additional environmental outcome has been set to address these requirements.
1. A flow regime that ensures no deterioration in Good Ecological Status and maintains the River Test and Lower Test Valley SSSIs and Solent & Southampton Water Ramsar habitats and species.
Since the Environment Agency and Southern Water disagree about the risk of the impact of the fully licence abstraction licence on the River Test, no agreed locally derived bespoke target flow regime for the River Test has been developed. In the absence of an agreed alternative EFI is used as the default flow objective in order to test if any licence we derive poses a risk of deterioration under WFD. Therefore, a flow regime to meet EFI is required to manage the WFD risk of deterioration to the designated ecology and to meet the River Test SSSI objectives and maintain the Ramsar habitats.
4.2 Flow Data The environmental allocation of the ALS resource assessment is calcauted as a percentage of natural flow. Therefore natural flow is needed for the Ledger. The Ledger also uses gauged flow to compare with its own “denaturalised” flow scenario or “Recent Actual” to make sure that the assumptions on artificial impacts in the Ledger are correct. This section describes the used in the Ledger for the Lower Test APs.
4.2.1 Gauged Data The 2013 ALS ledger includes gauged flow for the period 1990-2007. During the RSA/NEP agreed data set DG100 defined flow for distinct locations (Figure 4.2-1). So for the 2017 Test & Itchen ledger update we decided to be consistent with those data used in the RSA/NEP project. However, we needed to assess the significance of any differences between these and the current data.
Figure 4.2-1 Location of flow data points Hydrology Assessment June 2017
Flow statistics for the D100 locations were produced and compared to those of the ALS APs which are co-located with the DG100 locations, i.e. A15 Blackwater Total, AP16 River Test Total, and AP18 Ower. The AP15 and AP16 locations are ungauged sites and so the flows at these had to be estimated using upstream gauges. Table 4.2-1 shows how the gauged flows for each site were calculated.
Table 4.2-1 Derivation of gauged flow for DG100 (and ALS 2017) Lower Test flow sites Site Easting Northing Data Source Site A Main Test u/s of Little-Great split 435460 116340 Broadlands GS MINUS Test Back Carrier GS Site B Great Test imm d/s Little Test split 435404 115925 Site A minus flow at Conagar Bridge GS Site C Great Test d/s Nursling Abstraction 435170 115786 Site B minus Nursling Fish Farm abstraction Site D Great Test d/s Testwood Abstraction u/s Blackwater confluence 435430 115248 Testwood GS Site E Great Test d/s Blackwater confluence 435559 115171 Site D plus flow AP15 River Blackwater Total flow Site E plus Nursling Fish Farm abstraction Site F Great Test at MRF location 435708 115172 (representing its discharge) AP18 Ower GS (Blackwater AP) 432854 117412 Ower GS Site H Little Test 435515 115899 Conagar Bridge GS plus Test Back Carrier GS Not actually in DG100 spreadsheet but would be AP16 River Test Total AP (Great and Little) 436885 113674 Site F plus Site H
ALS point for reference as flow entering the Lower AP14 Timsbury Bridge AP 435126 123402 Test system. Based on spot flow gaugings at GS. Not officially a location in DG100 but would be Ower GS catchment factorised to the M27 Blackwater GS (Ower 104 km2, confluence 146 km2) plus the flow of the Broadlands Fish Farm Carrier as recorded at M27 TV1 Gauging station AP15 River Blackwater Total (AP) 435409 115156 and hind cast using gaugings.
The differences between the ALS old set of gauged flows and the DG100 gauged flows can be seen in Figure 4.2-2 and it appears that the DG100 dataset produces higher flows than the old ALS 1990-2007, especially at AP16. There are two possible reasons for the differences:
using different time periods (change is climate or change in catchment conditions) Method of estimating flows for the ungauged sites
The Ower GS is the only AP at a permanent gauge and its flows are considered natural, therefore the difference between the 1990-2007 statistics and DG100 flow statistics will due to changes in timeperiod and not method of estimating flows. Figure 4.2-2 shows that Ower’s DG100 statistics are higher and so there is a difference in using the different time periods.
AP16 is an ungauged site and there is a large difference between the two sets of data statistics as seen in Table 4.2-1. There is a difference in the method of estimating the flows at this site. The ALS statistics combine the flow statistics of each upstream gauge (due to the short record of the Broadlands FF Carrier) while the DG100 dataset uses continuous timeseries data because its record starts in 1996 to co-inside with the start of the Broadlands FF Carrier record. In order to directly compare the methods and to take out the timeperiod bias that Ower GS showed, the ALS method was applied to the DG100 1996-2015 timeperiod. The comparable statistics show that that the different methods of estimating the ungauged statistics do have an influence on the statistics but appear to only explain part of the large difference between the 1990-2007 statistics and DG100.
Hydrology Assessment June 2017
1300 1208 1180 1200 1100 1068 1000 900 800 700 600 481 500 415 Gauged (Ml/d) Flow 400 363 300 195 209 200 78 88 100 64 71 12 9 0 AP18 Ower GS AP15 Blackwater Total AP16 River Test Total
CAMS 1990-2007 Mean Flow DG100 1996-2015 Mean Flow DG100 1996-2015 data using CAMS method Mean Flow CAMS 1990-2007 Q95 DG100 1996-2015 Q95 DG100 1996-2015 data using CAMS method Q95
Figure 4.2-2 Comparison of DG100 1996-2015 flow statistics with ALS 1990-2007 statistics
Therefore, there are other catchment factors at play influencing the gauged flows. Comparing the timeperiod gauged flows of the gauges used in estimating the ungauged flows of AP16 (Ower GS, Conagar Bridge GS, Testwood GS and Test Back Carrier GS) the biggest differences are at Testwood GS (Figure 4.2-3) particularly at low flows.
Figure 4.2-3 Testwood GS flow statistics for 1996-2015 compared to 1990-2007
The Testwood abstraction is located upstream of the Testwood GS and so the difference in low flows could be to do with a change in the operation of the abstraction. Comparison of average daily abstraction rates over the two timeperiod (Figure 4.2-4) shows that there is a significant difference in abstraction especially during the typical low flow months. Therefore, the lower rates of abstraction during 1996-2015 means less impact on flows leading to higher gauged flows.
Both sets of data are equally suitable for use in the resource assessment, but since 1996- 2015 reflects a more recent time period, which includes a more recent representation of the operation of the Testwood licence then it was decided that the DG100 data would represent the flow statistics of AP15, AP16 and AP18 in the ALS 2017 ledger Hydrology Assessment June 2017
Testwood Average Daily Abstraction Rates for periods 1990-2007 and 1996-2015 80.0 Average daily abstraction 1990-2007 Average Daily Abstraction 1996-2015 75.0
70.0
65.0
60.0 Abstraction rate (Ml/d) rate Abstraction
55.0
50.0
Jul/09
Jan/09
Jun/09
Oct/09
Apr/09
Feb/09 Sep/09
Dec/09
Aug/09
Nov/09 Mar/09 May/09 Figure 4.2-4 Comparison of average daily rates of Testwood Abstraction for 1990-2007 and 1996-2015
It is important to note that since the DG100 dataset produces more flow than the previous ALS standard period statistics of 1990-2007 the results of the RAM may differ from previous version of the ledger. The 2017 assessment is the definitive assessment to be used for the licence change proposal.
It has also been noted that the ALS does not appears to have included the flow from the Test Back Carrier, though it contributes only a small proportion (0% at Q95) to the overall Test Total flows so won’t have been the reason for the variation between methods. The ALS 2017 ledger flows include the Test Back Carrier to be consistent with the DG100 dataset.
4.2.2 Natural Data The underpinning data for a resource assessment is natural flow data since the water available for abstraction is the difference between natural flow and the environment need (EFI). The ALS ledger includes a natural flow dataset while the DG100 dataset does not.
The derivation of the ALS natural flows is described for each AP in the “ALS Conceptualisation Report 2012”. In summary, the 2013 ALS ledger naturalised gauged flow by using the abstraction impact (model natural flow minus model gauged flow) from the Test & Itchen Groundwater (TIGW). The 2013 method allowed for a better representation of flow variability than simply using the modelled flows.
Natural flows are available in the 2013 ledger. Flows entering the Lower Test system are natural; AP14 Timsbury gauged flows are the same as natural (figure 4.2-5). However, the natural flows need to match the updated gauged flows for the two Lower Test APs and so need to be estimated for the DG100 time period of 1996-2015 and using the assumptions of that data set. The main assumptions differing from the ALS natural flow data is that the “current” hydrological system setup of braided channel and flow splits of the Lower Test, as seen in Figure 3-1, are considered “natural”. So the natural flow of AP15 Blackwater should include the Broadlands Fish farm carrier flow, and the flow upstream of the Great-Little Test split would not naturally include the Test Back Carrier, and lastly that while the Great-Test Little Test split is managed by sluices the flows into the channels are natural. Hydrology Assessment June 2017
Figure 4.2-5 Flow accretion profile from TIGW model for the Test (Timsbury is just upstream of the Broadlands Fish Farm) and AP14 Timsbury ALS Flow Duration Curve (top right)
Therefore the natural flows for the latest 2017 ALS to match the DG100 gauged flows timeperiod are produced as described in Table 4.2-2. The differences between the ALS old set of gauged flows and the DG100 gauged flows can be seen in Figure 4.2-6.
Table 4.2-2 Derivation of natural flow using DG100 assumptions for Lower Test flow sites Site Easting Northing Data Source Site A Main Test upstream of Little- Great split 435460 116340 As gauged flow Site B Great Test imm d/s Little Test split 435404 115925 As gauged flow Site C Great Test d/s Nursling Abstraction 435170 115786 same as Site B Site D Great Test d/s Abstraction u/s Testwood GS + Testwood abstraction + Blackwater 435430 115248 Nursling FF abs Site E Great Test d/s Blackwater Site D plus flow AP15 River Blackwater confluence 435559 115171 Total flow natural Site F Great Test at MRF location 435708 115172 As Site E AP18 Ower GS (Blackwater AP) 432854 117412 As gauged flow Site H Little Test 435515 115899 As gauged flow AP16 River Test Total AP (Great and Little) 436885 113674 Site F plus Site H AP14 Timsbury Bridge AP 435126 123402 As gauged flow AP15 River Blackwater Total (AP) 435409 115156 As gauged flow
It can be seen from Figure 4.2-2 that the DG100 statistics produce higher flows than the ALS, especially at AP16.
Hydrology Assessment June 2017
1300 1265 1173 1200 1143 1100 1000 900 800 700 600 542 534 500 436 400 Gauged (Ml/d) Flow 300 209 200 115 78 88 71 100 12 9 17 0 AP18 Ower GS AP15 Blackwater Total AP16 River Test Total CAMS 1990-2007 Mean Flow DG100 1996-2015 Mean Flow (AP16 flow using naturalised Testwood GS) DG100 1996-2015 Mean Flow (AP16 flow from ungauged flow at Testwood GS) CAMS 1990-2007 Q95 DG100 1996-2015 Q95 (AP16 flow using naturalised Testwood GS) DG100 1996-2015 Q95 (AP16 flow from ungauged flow at Testwood GS)
Figure 4.2-6 Comparison of DG100 1996-2015 natural flow statistics with ALS 1990-2007 natural flow statistics
As discussed in the gauged data section the differences between the dataset flow statistics are due to the different time periods used and different methods in estimating the ungauged sites. However, the differences are not as large as the gauged flows.
The added complexity in the natural flows estimation for the AP16 however it that there are two ways of estimating the natural flow of the Testwood GS location. The first is to naturalise the site by adding the abstraction quantities of Testwood and Nursling Fish Farm back onto the Testwood GS gauged flows, and the second is by subtracting the Little Test flow at Conagar Bridge GS from the estimated ungauged flow upstream of the Great-Little Test flow split (Broadlands GS – Test Back Carrier). The difference between the naturalisation methods can be seen in Figure 4.2-7 that naturalised Testwood GS produces higher flows.
The reason for more flow at Testwood GS is likely down to accretion from the surrounding catchment as there are a series of field drains and small channel between the Little-Great Test split and Testwood GS. Using the upstream ungauged flow assumes no accretion is accounted for. So using the Testwood GS provides actual data at the site and is the better option. Therefore, this was the method used for the 2017 ALS update. Getting the natural flow right at the Testwood GS location is vital as it has knock-on effect for the natural flows used downstream at AP16.
It is important to note that since the DG100 dataset produces more flow than the previous ALS standard period of 1990-2007 the results of the RAM will differ from previous version of the ledger. The 2017 assessment however is the definitive assessment for the licence change proposal.
Hydrology Assessment June 2017
Natural Flow timeseries at Testwood 45
40
100.000 35
30
25
Flow Flow (m3/s) 20
15
10
5
0
Title
Natural Flow of Grest Test at Testwood using u/s gauges Natural flow of Great Test at Testwood using abstraction
Flow(m3/s) 10.000
1.000 0 10 20 30 40 50 60 70 80 90 100 Percentile Natural Flow of the Great Test using u/s ungauged flows Natural Flow of the Great Test at Testwood using GS and abstraction data Figure 4.2-7 Naturalised flow timeseries for furthest downstream point of Great Test (at Testwood GS)
4.3 Artificial Influences The ALS ledger includes all licensed abstraction – groundwater and surface water, in a ALS catchment. The 2017 Ledger updated the list of abstraction licences in the test & Itchen and checked that the discharges listed are still active.
As stated in section 4.2.2 the flows at Timsbury are considered natural and so any impact seen at AP16 is due to abstraction between those locations. There are a five consumptive surface water abstraction between Timsbury and AP16 of which the largest by far is the Testwood Public Water Supply surface water licence 11/42/18.16/546 whose details can be seen in Table 4.3-1 below. This licence accounts for over 99% of consumptive surface water licensed quantities in the whole Test catchment with the remainder being spray irrigation licences. The summer spray irrigators between Timsbury and AP16 amount to a combined total daily rate of 4 Ml/d which is less than 3% of the Testwood licensed daily abstraction rate. They are all located on the River Test proper around Romsey and so they impact on the Total flow of the Test.
Table 4.3-1 Testwood Licence details Licence Number Licence Holder Details Location Maximum abstraction Purpose (name and address) (NGR) quantities (Ml/d)
Southern Water Services SU 3529 49,915 Ml/year Public water Ltd 1533 136 Ml/d supply Yeoman Road 6 Ml/hour 11/42/18.16/546 Durrington West Sussex BN13 3NX
Flow Condition: The Authority shall cease or reduce rate of abstraction hereby authorised so as not to cause either the flow in the River Test downstream of the Testwood Pumping Station intake as measured at SU 359 150 or the aggregate of:- The flow in the River Blackwater as measured at Ower GS, and The flow in the River Test downstream of the Testwood Pumping Station intake as measured by a gauge to be constructed by the Authority at SU 354 153 [aka Testwood GS], and The Flow in the Nursling Fish Farm carrier below Nursling Mill as measured at SU 351 158 to fall below 91,000 m3/d (91 Ml/d).
Hydrology Assessment June 2017
Figure 4.3-1 shows that use of the Testwood source has generally declined since our available records begin in 1989 and that the licence has normally been used at less than 50% of its maximum annual amount of 49,915 Ml/yr.
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1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 1989 Figure 4.3-1 Testwood annual abstraction 1989 – 2016
Figure 4.3-2 shows that the Testwood licence is typically used at around 50 – 60 Ml/d and has never been used at daily rates higher than 80 Ml/d in the last ten years. The annual licence quantity constraint would allow the current licence to be used at the full daily rate of 136 Ml/d on every day of the year. The only other constraint on the abstraction is the flow condition of 91 Ml/d (approx. 30% of Qn99 at the Great Test at MRF location).
Figure 4.3-2 Testwood daily abstraction 2007 – 2016
It was decided to profile the Testwood Licence impact in the Ledger in order to represent the abstraction. Figure 4.3-1 shows the profile used in the Ledger. Hydrology Assessment June 2017
Testwood Average Monthly abstraction profile
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An additional change to the 2017 ALS ledger is the removal of the Broadlands FF carrier “complex impact”. Previously the Broadlands FF carrier was treated in the ledger as an artificial influence since it impacts two different channels. However, with considering the Broadlands FF carrier as part of the natural flow of AP15, not just part of the gauged flow, then there is no need to have this “complex impact”.
4.4 Additional Assessment Points in Ledger The Testwood abstraction is located in the AP16 catchment which encompasses all of the River Test from Timsbury down to the estuary. It is also located in WFD waterbody GB107042016840 with the outflow point of that waterbody being at AP16. However, both of these assessment areas do not consider the local impacts on the many channels of the Test, because the modelling method cannot cope with the negative accretion that these splits cause. However, since the Testwood abstraction is located on the Great Test arm of the river it seemed prudent to assess its impact of the abstraction on the local river network not only the wider system so a “temporary” AP was created in the 2014 Ledger (DG100 Site D). Another temporary AP named Great Test AP (DG100 Site E) was also created to represent the influence of the River Blackwater on Great Test flows in order to also assess local downstream impacts of the abstraction (Figure 4.2-1). The flow data used for the two AP is as described in Tables 4.2-1 and 4.2-2.
5. Current Lower Test WR Assessment
The ALS uses the EFI to screen new abstraction licence applications to indicate where flow pressure may compromise the WFD ecological status and so set conditions to ensure sustainability. It can also be used to indicate where pressure may already be compromising the ecological status. To meet a flow regime that supports good then flows need to be above EFI at all time. Flow above EFI are available for abstraction and the Ledger produces Hands off Flows and suggest how much water available is above each HOF threshold, known as “takes” to be used. Scenario flows below EFI indicate can be used to indicate what water needs to be recovered.
Using the 2017 Ledger the EFI compliance for AP16 Test Total is shown in Figure 5-1. The ALS results show that recent actual flows are above the EFI and therefore current rates of abstraction are not having an impact on the flows reaching AP16. But the ALS results also show that at Fully Licensed rates of abstraction flows would only be above EFI for 72% of the time. So the current licence fully licensed flow regime fails to meet EFI and so does not meet the environmental outcomes of 2, 3 and 5.
Hydrology Assessment June 2017
Figure 5-1 ALS Assessment Results at AP16 Test Total
Table 5-1 shows a summary of the ALS results for all 3 assessment points considered for this report and it can be seen that while AP16’s recent actual (RA) flows are compliant with EFI the two upstream APs are not. So the current licence may have local impacts. Despite flows failing EFI in the Great Test, our own ecological evidence shows that under current rates of abstraction and current flow conditions there is no evidence of damage related to abstraction. In addition, invertebrates are achieving high status immediately downstream of the abstraction point. For those reasons, we have chosen not to apply licence conditions which would ensure flows meet EFI at all points on the Lower Test system.
Table 5-1 ALS results for the current Testwood Licence Conditions Reach % time EFI % time EFI Salmon HoF compliant FL compliant RA Target = flow above EFI 100% of the time AP16 Test Total 72% - fail 100% - pass Fail - Licence HoF is 91 Ml/d at MRF location which is lower than either Testwood GS 32% - fail 87% - fail salmon migration protection HoF
Great Test AP 59% - fail 97% - fail
The salmon migration protection flows (as % of QN99) will not be being met either since fully licensed flows fall below EFI from Q72 and the current flow condition on the Testwood licence of 91 Ml/d (29% of the QN95) is lower than the protected flows. So the current licence fully licensed flow regime does not satisfy environmental outcomes 1 either.
An added complexity at Testwood GS is the impact of the Nursling Fish Farm licence. Although the licence is still in place, the site is now disused and there is no longer a discharge consent to allow water from any fish farm activity to be discharged. A small amount of water passively flows into the site and subsequently enters a water meadow system which ultimately discharges to the Little Test. We are also working on changing the Nursling Fish Farm licence as removing this may improve the modelled local impact on EFI at Testwood GS. However, the Nursling licence change will not change the compliance at AP16 Test Total.
WFD hydrological assessments (referred to as Water Resources compliance) are reported for a waterbody outflow point for the Recent Actual scenario at the Q95 flow and flows above EFI at Q95 are considered to “support” Good Ecological Status (GES) of a waterbody. A hydrological regime must not compromise the achievement of good status and this includes Hydrology Assessment June 2017 preventing deterioration of water body status due to new abstractions. ALS helps to achieve the WFD by managing water resources by producing ALS and it by providing the underlying WR data for the WFD hydrology assessments.
The criteria used for WFD WR compliance can be seen in Table 5.4-2. The River Test ecology is considered to be moderately sensitivity to changes in flow so has an EFI relating to ASB2.
It must be noted that the Ledger works on Recent Actual and Fully Licensed scenario and on the full Flow Duration Curve (FDC) at an AP. It is not possible to reproduce the same 100 point FDC analysis in the WRGIS. So to simplify it for application in the GIS, approximate summary percentages are calculated: Q95, Q70, Q50 and Q30 for each waterbody (70_09 RAM 4 Part G guidance). Due to this the WFD assessments will only totally agree with the Ledger at Q95 which is why WFD WR compliance is made at only at Q95.
Table 5-2 WFD WR Criteria for compliance at Recent Actual Q95 Not adequate to support GES: High Flow not adequate to support GES: Low to Confidence (quite Supporting GES* Moderate Confidence (uncertain) certain) Abstraction Non-compliant Sensitivity Band Compliant with EFI Band 1 Non-compliant Band 2 Non-compliant Band 3 <10% lower than <35% lower than <60% lower than natural natural flow >60% lower than natural flow flow ASB3. high (<10% allowable natural flow (<25% below EFI) (<50% below EFI) sensitivity abstraction at ASB) <15% lower than <40% lower than natural flow <65% lower than natural >65% lower than natural flow ASB2. moderate (<15% allowable flow natural flow (<25% below EFI) sensitivity abstraction at ASB) <20% lower than <45% lower than natural flow <70% lower than natural >70% lower than natural flow ASB1. low (<20% allowable flow natural flow (<25% below EFI) sensitivity abstraction at ASB) *GES = good ecological status All % are for the Recent Actual scenario flow and % are for Q95 only
The most recent WFD WR data for GB107042016840 Lower Test from the WRGIS is seen in the table 5-2 below. The 2017 ledger has yet to be uploaded to WRGIS and therefore, the WRGIS WR assessment may differ slightly. A manual WFD WR assessment has been completed for the purpose of this report (Table 5-2). The WFD WR assessments shows that at Recent Actual levels of abstraction the waterbody outflow for GB107042016840 is compliant at Q95 (supports GES).
The WRGIS WR assessment also now models fully licensed flows though these are not reported in the RBMP. These manual results can be seen from Table 5-3 and show that at fully licensed the waterbody is non-compliant at Q95 and would not support GES. This indicates that there is a potential for deterioration between statuses if the licensed headroom were fully utilised.
Using the ALS AP data a WFD assessment can also be made for each of the two local APs at Q95 and can be seen in table 5-3 that Testwood GS would not be supporting GES at recent actual and both location would not be support GES at fully licensed, and so there is a potential risk of deterioration at those sites.
Hydrology Assessment June 2017
Table 5-3 WFD WR assessment results for GB107042016840 Lower Test and local reaches APs Q95 % % EFI RA FL Natural RA flow below FL flow below flow Compliance Compliance Stat Flow natural natural Ml/d Ml/d Ml/d Ml/d
<40% below 398.8 <15% below 296.5 natural = Non- WRGIS 432.4 367.5 8% natural = 31% Compliant Compliant (92% of 69% of Band 1 QN95) QN95 <40% below 497.1 <15% below 409.5 natural = Non- Test Total 542.5 461.1 8% natural = 25% Compliant (92% of Compliant 75% of QN95) QN95 Band 1 <40% below <65% below 235.1 natural = 109.3 Testwood natural = Non- 291.6 247.8 19% Non- 63% GS compliant (81% of Compliant 37% of Band 2 QN95) Band 1 QN95 <40% below 316.2 <15% below 229.8 Great Test natural = Non- 367.6 312.5 14% natural = 37% AP Compliant (86% of Compliant 63% of QN95) QN95 Band 1 RA = Recent Actual, FL = Fully Licensed
However, the Test (Lower) WFD water body (GB107042016480) is at Good Status under recent actual abstraction rates with invertebrates classified as high, fish and macrophytes classified as good, physico-chemistry and specific pollutants at good, and hydrology and morphology classified as supporting good status (EA, 2015). The WFD monitoring points however are upstream of the Testwood abstraction and so do not necessarily reflect the impact of the licence. The fish classification is also on the boundary of good and moderate and a slight change in salmon population scoring could cause a change in status so the WFD results do not tell the whole story. However, there is a local EA invertebrates monitoring point downstream of the abstraction and it shows recent actual abstraction rates are supporting good.
6. Licence Change Options No formal options appraisal for possible licence change has been carried out by Southern Water as part of this NEP funded RSA project.
This report will therefore consider the following licence change scenarios to feed into any options appraisal for the final proposed licence change(s): 1. Change licence to meet EFI (using ALS conditions) 2. Cap licence to Recent Actual Quantities 3. Replace current licence flow condition with salmon migration protection HoFs 4. Combine salmon migration protection HoFs with reductions in licence quantities 5. Change licence to Voluntary Licence conditions (2016) 6. Use non-licence change options – catchment management and affirm licence
The scenarios in this report will only take regard to the impact on hydrology as a supporting element of WFD.
Hydrology Assessment June 2017
6.1 Option 1: Change licence conditions to meet EFI
The ledger is used to licence “new” abstractions as it proposes flow conditions and sustainable abstraction quantities based on its resource assessment. If we were to treat the Testwood licence as “new” and remove it from the ledger then we can see what the proposed conditions of the licence would be to meet EFI at AP16 Test Total.
Figure 6.1-1 shows that the ALS ledger says that a “new” licence at AP16 would need a flow condition of 355 Ml/d which is the Minimal Residual Flow (MRF) (75% of QN99) and that the available water for abstraction before the need to step up to the next level of flow protection would be 81 Ml/d. All of the HOF takes are available to a new licence at AP16 since at Timsbury the RA and FL scenario are balanced out as mentioned previously.
When running the Testwood licence at 81 Ml/d with the MRF through the Ledger however, there was a slight breach in EFI due to the way other licences and complex impacts such as the upstream cressbeds interact in the modelling. Therefore, changing Testwood abstraction to be 80 Ml/d and 29,200 Ml/year with a 355 Ml/d flow condition at Test Total results in flows meeting EFI at all times at the outflow point of Test Total.
The recent actual average daily abstraction rate for Testwood is between 50-60 Ml/d (figure 4.3-2) and so a change to 80 Ml/d will not present a significant partial change the average current use of the licence. However, the proposed ALS conditions presents a higher level of protection via the HoF than the current licence and so it may restrict the licence more than in the past, changing the way the source can be used.
Table 6.1-1 AP16 Test Total Takes and HOFs with no Testwood licence AP16 2017 ledger AP16 2013 Ledger Ml/d Ml/d HOF6 Take 268.7 237.6 HOF6 1285.4 1173.6 HOF5 Take 106.8 89.6 HOF5 1018.5 949.7 HOF4 Take 63.1 53.0 HOF4 860.6 817.1 HOF3 Take 42.1 34.4 HOF3 755.1 731.0 HOF2 Take 43.5 37.8 HOF2 646.2 636.5 HOF1 Take 41.6 41.1 HOF1 542.5 533.9 MRF Take 81.4 79.6 MRF 355.6 352.9
The alternative, to a single licenced quantify and HoF and to allowing more abstraction staged hand of flows could be used – e.g. if the 136 Ml/d need is justified then the abstraction would be licensed so that the first 80 Ml/d could be taken as long as flow is 355 Ml/d or more (MRF condition) and then a further 41 Ml/d would be able to be taken when flows were above 542 Ml/d (HoF1) and the remaining water taken when flows were above 646 M/d (HoF 2). This is obviously very difficult (but not impossible) to manage operationally but is an option if the licence were being applied for today at 136 Ml/d.
While the 80 Ml/d might be sustainable at AP16 locally the flows at Testwood GS AP and the MRF AP are still below EFI at fully licensed, though flows have improved (Table 6.1-2).
Hydrology Assessment June 2017
Table 6.1-2 ALS results for the Testwood using ALS Conditions to meet EFI Scenario Testwood GS Great Test AP16 Test Total Target 1: flows above EFI 100% of the time = no deterioration Target 2: up to 15% reduction in natural flow at Q95 = Supports GES % time flow supporting % time Flow supporting % time Flow supporting flow as % GES at flow as % GES at flow as % GES at are of Q95 are of Q95 are of Q95 above QN95 above QN95 above QN95 EFI EFI EFI ALS @ 80 Ml/d With MRF 74% -22% Fail 100% +14% Pass of 355 32% -44% Fail Ml/d at In-river salmon migration Test Total salmon river entry HoF set as protection HOFs set as 265 (233 Ml/d at 390 ML/d = FAIL Great Test) Ml/d = FAIL
A WFD WR assessment using the ledger data also shows that the proposed ALS ledger conditions improve the hydrology to be compliant at AP16 at fully licensed Q95 (Table 6.1-2). But not change the compliance at the upstream APs.
The current flow condition of 91 Ml/d is based at the MRF AP, while the proposed is at AP16 Test Total. If we transpose the 91 Ml/d (25% of QN99) to AP16 then the current HoF would be the around 142 Ml/d at AP16 so we can instantly see that the there is a significant increase in protection of flows. Figure 6.1-1 compares the flows at AP16 to the ALS HoF and it can be seen that over the 20 year period flows would have fallen below the proposed 355 Ml/d for a short period in 2005 and 2006 while it didn’t fall below the current 91 Ml/d. So the new condition will restrict the abstraction more often.
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Test Total gauged Test Total natural CAMS MRF condition (355.6 Ml/d) River Entry HoF (390 Ml/d) Current Licence HoF transposed to AP16 Test Total (137 Ml/d) 137 Figure 6.1-1 AP16 flows compared to ALS proposed HoF, current licence HoF and Salmon Entry HoF.
However, restrictions during drought periods are dealt with through the drought process and ALS and WFD only consider the sustainability of licence under normal use. It is also noted that while the ALS proposed HoF is more protective than the current licence it still does not meet the salmon migration protection flows Therefore, using the ALS proposed licence conditions while meeting EFI does not meet the bespoke flow regime for the SSSI salmon.
Hydrology Assessment June 2017
6.2 Option 2: Change licence to Average Recent Actual Quantities Since the waterbody is at GES with current levels of abstraction, then an option is to cap the abstraction to those levels which are not causing deterioration. Recent actual rates as seen on Figures 4.3-1 and 4.3-2 are between 50-78 Ml/d and 18,000-25,000 Ml/year. On average the licence has used 21,700 Ml/year at an average rate of 60 Ml/d. Using these quantities in the ALS ledger for the licence (still using the 91 Ml/d flow condition) then the licence meets EFI at Q95 at Test Total but will fail EFI at flows lower than Q95 (Table 6.2-1).The proposed licence change also does not meet the salmon migration protection flow requirements and so does not meet all the environmental outcomes.
Table 6.2-1 ALS 7 WFD results for Testwood using Recent Actual and current HoF. Scenario Testwood GS Great Test AP16 Test Total Target 1: flows above EFI 100% of the time = no deterioration Target 2: up to 15% reduction in natural flow at Q95 = Supports GES % time flow supporting % time Flow supporting % time Flow supporting flow are as % GES at flow as % GES at flow as % GES at above of Q95 are of Q95 are of Q95 EFI QN95 above QN95 above QN95 EFI EFI Recent actual 87% -18% Fail 100% +11% Pass rate of 60 33% -39% Fail In-river salmon migration Ml/d with salmon river entry HoF set as 390 protection HOFs set as 265 Ml/d MRF of ML/d = FAIL 91 Ml/d = FAIL
However, even at 60 Ml/d the local APs at Testwood GS and the Great Test AP still show flows below the EFI although for slightly less of the time. The proposed reduction in licence quantity matches the average recent operation of the source but in contrast to option 3, actual abstraction patterns would be affected. In the last 10 years, daily abstraction has peaked at 77 Ml/d and annual abstraction at 22,287 Ml and so there is a need to retain some degree of reasonable operational flexibility within the licence.
6.3 Option 3: Change current HoF to the in-river salmon migration protection and salmon entry protection HoFs Option 3 is simply to replace the current licence 91 Ml/d flow condition with both salmon migration protection HoFs and keep the current licence quantities. The proposed salmon HoFs however, as set in environmental outcome 1, only set a flow for March through to December and suggest that in Jan and Feb a HoF is set based on EFI. The ALS suggests that to meet EFI then the MRF (75% of QN99) at the relevant assessment points should be applied. The 390 Ml/d is 82% of QN99 and 265 Ml/d is 85% of QN99. The complete environmental outcome 1 measures are:
• 390 Ml/d at Test Total from March through December and 355 Ml/d from January through February, and • 265 Ml/d at Testwood Bridge from March thought December and 233 Ml/d from January through February.
Using the salmon protection HoFs as replacements for the current licence 91 Ml/d MRF does not change the results of WFD WR assessment to support GES - it still fails and flows still fail to stay above the EFI at all times (Table 6.3-1). So although environmental outcome 1 to protect salmon migration is met, this option does not meet outcome 5 to ensure compliance with EFI.
Therefore the flow requirements need to be teamed up with a reduction in the daily and annual quantities of the licence such as in Option 1.
Hydrology Assessment June 2017
Table 6.3-1 ALS & WFD results for Testwood using 136 Ml/d and both Salomon migration protection HoFs. Scenario Testwood GS Great Test AP16 Test Total Target 1: flows above EFI 100% of the time = no deterioration Target 2: up to 15% reduction in natural flow at Q95 = Supports GES % time flow supporting % time Flow supporting % time Flow supporting flow are as % GES at flow as % GES at flow as % GES at above of Q95 are of Q95 are of Q95 EFI QN95 above QN95 above QN95 EFI EFI Current Fully 47% -37% Fail 72% -25% Fail Licence, 21% -64% Fail HOF 265 In-river salmon migration salmon river entry HoF set as Ml/d and protection HOFs set as 265 390 ML/d = PASS 390 Ml/d Ml/d = PASS
6.4 Option 4: Change current HoF to the in-river salmon migration protection and salmon entry protection HoFs along with a reduction in licence quantities to meet EFI
The salmon flow requirements need to be teamed up with a reduction in the daily and annual quantities of the licence such as in Option 1. Therefore, the proposal which could satisfy all the environmental outcomes is reducing the licence quantities to 80 Ml/d and 29,200 Ml/year with Hands off Flow from Mar to Dec of 390 Ml/d at Test Total & HOF of 265 Ml/d at Testwood Bridge and from January through February 355 Ml/d at Test Total and 233 Ml/d at Testwood Bridge
The salmon protection HoFs were applied all year rather than seasonally as the ledger cannot model them. Table 6.4-1 shows that the option still fails the EFI on the local reaches at Testwood GS and Great Test AP, but meets the EFI for Test Total.
Table 6.4-1 ALS & WFD results for Testwood using 136 Ml/d and both Salomon migration protection HoFs. Scenario Testwood GS Great Test AP16 Test Total Target 1: flows above EFI 100% of the time = no deterioration Target 2: up to 15% reduction in natural flow at Q95 = Supports GES % time flow Support- % time Flow Support- % time Flow Support- flow as % ing GES flow as % ing GES flow are as % ing GES are of at Q95 are of at Q95 above of at Q95 above QN95 above QN95 EFI QN95 EFI EFI ALS @ 80 Ml/d 74% 22% Fail 100% 14% Pass with both Salmon In-river salmon migration 32% 44% Fail salmon river entry HoF set as migration protection HOFs set as 265 390 ML/d = PASS protection Ml/d = PASS HoFs
To assess the restrictiveness of the proposed licence changes then we can apply the in-river salmon migration protection flow of 265 Ml/d and 233 Ml/d to the fully licensed scenario flows of the Great Test AP, to see if and when flows would have fallen below the flow constraints and how much abstraction would have been possible. Similar results would be expected if assessment was made against the Test Total flow condition, which is generally slightly less restrictive than the Great Test flow condition based on current flow splits.
Figure 6.4-1 shows the scenario flow for abstraction at the proposed 80 Ml/d rate and it can be seen that there are short periods of time in 1996, 1997, 2005 and 2006 when abstraction Hydrology Assessment June 2017 would have ceased (after being ramped down) in order to meet the In-river salmon migration protection HoF condition.
Figure 6.4-2 shows the total annual abstracted quantities possible for the proposed abstraction rates when the salmon flow requirements are applied. It can be seen that the proposed annual for the 80 Ml/d scenario would only have been met 12 out of the 18 years of the study 1996-20141 but compared to the recent actual annual abstraction then the 80 Ml/d totals meet those in all years except for 2005, where the annual is short by 400 Ml/d (1% of the annual).
It must be noted that this flow condition analysis is based on semi-natural Testwood flows and so includes any impacts on the Great Test of the Nursling Fish Farm. Given at the Fish Farm is now disused the same magnitude of failures are unlikely to occur at those flows which will help the Testwood annual abstraction when demand is highest.
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1 Period is only up to 2015 as while there is abstraction data the 2015 flows are not complete for the year due to changes in the Broadlands Fish Farm carrier flows meaning that water levels in the M27 TV1 gauge fell below the recordable and no modelling was able to be carried out to complete the timeseries in the time frame available to this report. Hydrology Assessment June 2017
Testwood Licence annual abstraction using proposed 80 Ml/d quantity and Salmon Migration Protection HoF 35000
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2011 2014 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2012 2013 Actual Annual Abstraction Annual Abstraction at Proposed 80 Ml/d and salmon migration protection HoFs Average Recent Actual Annual Quantity (1989-2015) Proposed Max Annual Licensed Quantity @ 80 Ml/d Figure 6.4-2 Annual abstraction quantities for the 80 Ml/d option using the salmon migration protection HoFs compared to actual annual volumes
6.5 Option 5: Change licence to Voluntary Licence conditions In August 2016 Southern Water volunteered to modify their Testwood licence by making reductions to the annual quantity and proposing new monthly conditions to restrict abstraction. In addition, they proposed conditions linking higher rates of abstraction to low flow periods on the River Itchen when their abstraction licences on the River Itchen would be reduced. The main features of Southern Water’s application are:
i. To reduce the annual volume from 49,915Ml to 30,000 Ml. ii. To reduce the normal maximum daily abstraction from 136Ml to 105 Ml. iii. To add three-monthly volume limits of 8000 Ml for the three month periods commencing 1st March, 1st September, and 1st December and 9000 Ml for the three month period commencing 1st June. iv. When flows in the River Itchen fall to 230 Ml/d as measured at Allbrook and Highbridge gauging station and, on condition that demand restrictions have been implemented in line with the company drought management plan, allow abstraction at Testwood to increase to 136 Ml/d. v. To time limit the new licence to 2027, with presumption of renewal. vi. Between 2016 and 2027, commitment to the attached schedule of further reviews and licence changes.
It is only possible to model conditions 1 and 2 of the voluntary changes in the Ledger. The Ledger result for the voluntary licence, which still includes the 91 Ml/d flow condition at the MRF site, is that the EFI is only met 87% of the time at Test Total (Table 6.5-1). Although the EFI is only marginally failed at Q95 at lower flows, flows fall further below EFI and notably the MRF flow condition of 75% QN99 is not met and so environmental outcome 4 is failed. The existing flow condition of 91 M/d also fails environmental outcome 1 for the salmon protection and it is uncertain if environmental outcome 2 to protect the temperature Hydrology Assessment June 2017 regime for salmon would be met. Therefore, this option does not satisfy the environmental outcomes.
Table 6.5-1 ALS results for the voluntary Testwood Licence Conditions Scenario Testwood GS Great Test AP AP16 Test Total Compliance Target 1: flows above EFI 100% of the time Compliance Target 2: up to 15% reduction in natural flow at Q95 % time % of Compliance % % of Compliance % % of Compliance flow QN95 time QN95 time QN95 are flow flow above are are EFI above above EFI EFI Voluntary Licence 73% 23% Fail 87% 15% Fail Rate at 30,000 32% 46% Fail Ml/d at 91 In-river salmon migration salmon river entry HoF set as Ml/d MRF protection HOFs set as 265 390 ML/d = FAIL Ml/d = FAIL
Therefore while the proposed annual licence of 30,000 Ml is close to the EFI proposed annual of 29,200 Ml/d, this option can still draw flows below the EFI based on the maximum daily quantity, and its 91 Ml/d flow condition does not meet the salmon migration protection HoFs. This option does not meet any of the environmental outcomes.
It must also be noted that the Ledger uses the average annual quantity where the daily is higher. In this case where the voluntary daily rate of 105 Ml is more than the proposed annual of 30,000 Ml, then the ledger models the abstraction which is up to an average rate of around 82 Ml/d (based on its profile) in order to fit the annual above the HoF condition. Therefore, the full impact of 105 Ml/d is not technically being modelled, but regardless the licence change still does not meet all the environmental outcomes.
Figure 6.5-1 Voluntary licence change ALS ledger assessment for AP16 Test Total
Hydrology Assessment June 2017
6.5 Option 6: Alternative Management – Flow Splits Where there is a risk of deterioration identified as a result of abstraction, our guidance suggests that mitigation could be considered as an option to temporarily offset that risk.
Although Southern Water have been considering catchment management options and ways to modify flow splits in the Lower Test system, no firm options have been proposed.
For completeness in our Option Appraisal we have undertaken a sensitivity analysis to assess whether there is any real benefit in managing the flow diversions. However, flow diversions in the lower Test area are unlikely to have a significant effect on total flows entering the estuary, those which will attract salmon, and so although they may be worth considering as mitigation for local impacts, they will not be effective in mitigating any impacts on freshwater flows attracting fish from the estuary to the river.
The sensitivity analysis scenarios are based on managing the two main flow diversions on the Test: the Broadlands Fish Farm Carrier flow and Great-Little Test flow split. Three scenarios are modelled: i. reduce flow of the Broadlands Fish Farm Carrier by 60%, 1 2 ii. fixed /3: /3 split for the Great-Little Test 1 2 iii. reduce flow of the Broadlands Fish Farm Carrier by 60%, and fixed /3: /3 split for the Great-Little Test
Any benefits are assessed by looking at the change in flow reaching the Testwood abstraction on the Great Test.
6.5.1 Methodology: Reduce Broadlands Fish Farm Carrier flow by 60% The reduction in flow of the Broadlands Fish Farm Carrier is under the control of the Broadlands Estate. The Estate agreed to trial a change in flow of the carrier. Figure 6.5-1 below shows the actual data of that trial and shows that flows were reduced as low as 76% below average. The significant reduction in flow has dropped water levels to below those able to be physically recorded at the M27 TV1 gauging station, so no continuous flow record of the Carrier at the reduced flows is available for any analysis.
Broadlands Fish Farm Carrier (and M27 TV1) spot gaugings - change in flow split 1.800
1.600
1.400 + 22% LTA
1.200 -30% LTA +11% LTA
1.000
-30% LTA
Flow Flow (m3/s) 0.800
0.600 -34% LTA -27% LTA -43% LTA
0.400 -56% LTA -59% LTA
0.200 -70% LTA -69% LTA -76% LTA
0.000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1998-2016 inc. LTA Monthly Mean Flow (m3/s) 2016 Monthly 6.5-1 Broadlands Fish Farm Carrier 2016 trial flow compared to Long Term Average Hydrology Assessment June 2017
Decreasing the Broadlands Fish Farm Carrier will: increase flows in the Main Test above of the Great-Little Test split and therefore increase flows into the Great Test and Little Test, increase flows reaching Testwood intake, decrease flows river Blackwater reaching the confluence of the Great Test which may affect flows downstream of the Blackwater confluence with the Great Test not change the flows reaching AP16Test Total (balance of flows stays the same)
Natural flows were derived, as described in section 4.2, and scenario flows derived as shown in Table 6.5.1 below.
Table 6.5.1-1 Derivation of natural scenario flows for reduction of Broadlands FFC flows by 60% (still using DG100 assumptions and timeperiod) Eastin Northi Site g ng Data Source Testwood GS Natural (Testwood GS gauged + Testwood Abstraction + Nursling FF abstraction) Site A Main Test upstream of Little- + Conagar GS + Current Broadlands FFC flow – Great split 435460 116340 60% reduced BFFC flow Site A distributed using current flow split ratio Site D Great Test d/s Abstraction u/s between Conagar Bridge and Testwood GS Blackwater 435430 115248 Natural Site E Great Test d/s Blackwater Site D plus flow AP15 River Blackwater Total confluence 435559 115171 flow natural AP18 Ower GS (Blackwater AP) 432854 117412 Ower GS Natural flow Site A distributed using current flow split ratio between Conagar Bridge and Testwood GS Site H Little Test 435515 115899 Natural + Test Back Carrier AP16 River Test Total AP (Great and Site E + Nursling FF abstraction (as discharge) + Little) 436885 113674 plus Site H Ower factorised + 60% reduced Broadlands FFC AP15 River Blackwater Total (AP) 435409 115156 flow
6.5.2 Methodology: Coleridge Award Fixed flow split As discussed previously, following a dispute between milling and angling interests the flow split between the Great and Little Test was set by legally binding arbitration in 1931 (the Coleridge Award) which allowed one third of flow through the Little Test and two-thirds along the Great Test. The flow split is controlled by Conagar Sluice and is reasonably stable, but under very low flow conditions, more than one third of the flow has been measured in the Little Test at Conagar Bridge GS (Figure 6.5.2-1). Figure 7.2-1 also shows that on average the Little Test split is actually below the 33% split though it has been increasing slowly. So under the current hydrological system the Great Test actually gains more than its allocated two thirds flow on average. However, on a seasonal basis there is quite a variation in the split and it seems high flows seeing the least proportion of total flow (around 15%) on the Little Test while low flows see the higher proportion with up to a 50% portion of the flow in 1998 and 2005- 2006 (our last drought period).
It is the low flow proportion bias that causes the greatest issue to the Testwood intake as it means less water available when most needed. Therefore, it has been proposed that the split should be maintained as per the Coleridge Award as that will change the amount of flow reaching the Testwood intake particularly at low flow.
Hydrology Assessment June 2017
60% Little Test Flow Split as % of Total Test upstream of flow split
50%
40%
30%
20% 1/3 split Percentage Percentage Flow Split
10%
0%
Jul02 Jul10 Jul96 Jul97 Jul98 Jul99 Jul00 Jul01 Jul03 Jul04 Jul05 Jul06 Jul07 Jul08 Jul09 Jul11 Jul12 Jul13 Jul14 Jul15
Jan 96 Jan 97 Jan 98 Jan 99 Jan 00 Jan 01 Jan 02 Jan 03 Jan 04 Jan 05 Jan 06 Jan 07 Jan 08 Jan 09 Jan 10 Jan 11 Jan 12 Jan 13 Jan 14 Jan 15 Jan
Little Test Split at Conagar Bridge GS Coleridge Award one third split
Figure 6.5.2-1 Little Test Flow Split at Conagar Bridge GS as percentage Total Natural Flow upstream of split (*Natural flow = Conagar Bridge GS + Testwood GS Natural)
Natural flows were derived, as described in section 4.2, and scenario flows derived as shown in Table 6.5.2-1 below.
Table 6.5.2-1 Derivation of natural scenario flows for (still using DG100 assumptions and timeperiod) Eastin Northi Site g ng Data Source Testwood GS Natural (Testwood GS gauged + Site A Main Test upstream of Little- Testwood Abstraction + Nursling FF abstraction) Great split 435460 116340 + Conagar GS Site D Great Test d/s Abstraction u/s Blackwater 435430 115248 2/3rd of Site A Site E Great Test d/s Blackwater Site D plus flow AP15 River Blackwater Total confluence 435559 115171 flow natural AP18 Ower GS (Blackwater AP) 432854 117412 Ower GS Natural flow 1 Site H Little Test 435515 115899 /3 of Site A + Test Back Carrier AP16 River Test Total AP (Great and Site E + Nursling FF abstraction (as discharge) + Little) 436885 113674 plus Site H AP15 River Blackwater Total (AP) 435409 115156 Ower factorised + Broadlands FFC flow
6.5.3 Reduce Broadlands Fish Farm Carrier Flow and use Coleridge Award Fixed flow split Both reducing the Broadlands Fish Farm Carrier Flows and fixing the flow split increases the QN95 at Testwood GS which improve the ALS and WFD results slightly although do not change the WFD WR non-compliance . The two scenarios could therefore be combined to try and maximise the benefits provided. The derivation of the scenario flows are described in Table 6.5.3-1 below.
Hydrology Assessment June 2017
Table 6.5.3-1 Derivation of natural scenario flows for reducing Broadlands Fish Farm Carrier Flow and using the Coleridge Award Fixed flow split (still using DG100 assumptions and timeperiod) Site Easting Northing Data Source Testwood GS Natural (Testwood GS gauged + Testwood Abstraction + Nursling FF Site A Main Test upstream of abstraction) + Conagar GS + Current Little-Great split 435460 116340 Broadlands FFC flow – 60% reduced BFFC flow Site D Great Test d/s Abstraction u/s Blackwater 435430 115248 2/3rd of Site A Site E Great Test d/s Blackwater Site D plus flow AP15 River Blackwater Total confluence 435559 115171 flow natural AP18 Ower GS (Blackwater AP) 432854 117412 Ower GS Natural flow 1 Site H Little Test 435515 115899 /3 of Site A + Test Back Carrier AP16 River Test Total AP (Great Site E + Nursling FF abstraction (as discharge) and Little) 436885 113674 + plus Site H Ower factorised + 60% reduced Broadlands AP15 River Blackwater Total (AP) 435409 115156 FFC flow
6.5.4 Alternative Management Option Results The scenario flow duration curves are shown in Figure 6.5.4-1. The flow statistics show that each scenario increases the low flows at Testwood GS to above what is current naturally seen, which means more water is available naturally at the intake. Table 6.5.4-1 show a more detailed look at the mean flows and Q95 statistics for each location and each scenario. It can be seen that while low flows at Testwood might increase its mean flows can be decreased.
Each scenario naturalised flow statistics were used in the Ledger to assess any change in EFI compliance of the current Testwood licence and the results are summarised in Table 6.5.4-1 below. It can been seen that only the reduction in Broadlands Fish Farm Carrier flow has any positive affect on the EFI compliance, and this only a +1% change in time above EFI which is not significant. The fixed flow split, in fact, makes the overall flow compliance with EFI worse at Testwood GS and Great Test AP. This is because the current flow system biases flow to the Great Test throughout the majority of the flow regime and so it gets more than two thirds of the Total Test on average. When fixing the split, the flow is rebalanced and average Great Test flow decrease even though low flows flow are higher. What affect this reduction in average flow might have on the average use of the abstraction is not modelled in this report but is a consideration if this option was employed in the future.
The alternative management options therefore increase the low flows of the Great Test but do not mitigation the licence’s impacts on the Test Total nor Great Test flows. The scenario flow results however, could be used alongside a licence quantity change to improve the amount of flow available to the abstraction. The higher flow may also delay the employment of the proposed flow restrictions of any of the licence change options.
Hydrology Assessment June 2017
10000.0
1000.0 Flow(m3/s)
100.0 0 10 20 30 40 50 60 70 80 90 100 Percentile Testwood GS natural using 60% Broadlands Fish Farm Carrier Testwood GS natural using 2/3 flow split Testwood GS Nat using 2/3 splits and 60% reduction in Broadlands Fish Farm Carrier Testwood GS batural flows current system Figure 6.5.4-1 FDCs for each alternative management scenario at Testwood GS
Table 6.5.4-1 Flow sensitivity analysis summary results % of Current System Flows % time above EFI (target 100%) Natural Natural Natural BFFC Natural Natural BFFC Natural Flow: Flow: BFFC Flow: BFFC reduction Flow: Flow: reduction Flow: Location Stat Current reduction reduction Natural Fixed Current Natural Fixed System & Fixed & Fixed Flow Split System Flow Split Ml/d Flow split Flow split Testwood Q95 292 8% 7% 14% 32% - 33% - fail 19% - fail 19% - fail GS MF 822 5% -14% -11% fail Great Q95 368 -3% 6% 2% 59% - 59% - fail 35% - fail 35% - fail Test AP MF 1031 -1% -11% -14% fail
7. Change in Abstraction Sensitivity and EFI for the Test
7.1 ASB3 High Sensitivity While this is not a licence change option this section assesses the implication of this change on the Testwood licence and the proposed changed to the Testwood licence. The sensitivity of certain biological (namely fish) elements to changes in flow is being re-considered nationally. It is possible that the ASB banding for the Test is too low and that it should be set to an ASB3 – high sensitivity. This means that the allowable abstraction for the catchment would be reduced from 15% at Q95 to 10%.
The ASB was changed in the Ledger from 2 to 3 and as expected the EFI was met less of the time; 52% rather than 72% (Figure 7.1-1). When taking the Testwood licence out of the modelling to see what the ALS assessment would propose for a “new” licence to satisfy EFI then the water available for abstraction (after all upstream abstraction is considered) would be 58 Ml/d at Q95 compared to the 80 Ml/d available under ASB2 (section 6.1). This proposed licenced quantity reduction is below the average recent actual quantity of the licence and so would present a significant restriction on the PWS abstraction.
Hydrology Assessment June 2017
7.1-1 AP16 Test Total Compliance with current Testwood licence and ASB3.
7.2 ASB13 Transitional waterbody
While this is not a licence change option this section assesses the implication of a change in ASB on the Testwood licence. Southern Water’s consultant Atkins have suggested that a transitional waterbody EFI should be applied to the Test APs since the structures downstream of Testwood GS back up water and tidal influence is seen at the GS (Table 4.1.1-2).
Table 7.2-1: Percentage allowable abstraction from natural flows at different transitional waterbody abstraction sensitivity bands. Abstraction Sensitivity Band Q95 ASB13. 25% estuary inflow high sensitivity ASB12. 30% estuary inflow & marginal catchments mod sensitivity ASB11. 35% estuary inflow low sensitivity
If a transitional ASB were to be used for the upper Test estuary then the highest sensitivity would be used due to the need to protect flows for the SSSI migratory fish and flows out the Ramsar, SAC and SPA. ASB13 is the highest band and allows 25% of natural flow to be available for abstraction compared to the riverine ASB 2 which allows only 15%. When changing the ASB in the Ledger to 13 rather than 2 the AP16 Test Total still fails the meet EFI at all times, though it increases the time above EFI to 82% of the time (figure 9.2-1) from 72% of the time. So the licence would still need to be changed to meet EFI if a transitional ASB was used. However, as discussed previously the River Test SSSI flows need to be protected in particular to encourage, attract and maintain fish migration and the flow to be protected are higher than those required by the ASB2 EFI.
7.2-1 AP16 Test Total Compliance with current Testwood licence and ASB13. Hydrology Assessment June 2017
8. Conclusions
Southern Water’s Testwood licence (11/42/18.16/546) allows up to 136 Ml/d to be abstracted from the River Test SSSI. Typically the source has only been used at 40-50% of its licensed capacity. Existing recent actual abstraction rates (over the last 10 years) are broadly acceptable with regard to the invertebrates and macrophyte communities, although they marginally increase the risk to salmon migration over naturalised conditions. The WFD Lower River Test waterbody that the Testwood licence sit in is currently at Good Ecological Status.
Substantially increased abstraction quantities, or frequency of abstraction, during low flow periods could impact SSSI species, particularly salmon populations which are a key SSSI species. Increased volume or frequency of abstraction could reduce flows in the lower River Test system during exceptionally low flow conditions by up to 80%. Given that such potential impacts may occur in sequential years, there is a great deal of uncertainty over the impacts on the ecology.
No formal options appraisal for licence changes was carried out by Southern Water as part of this NEP funded RSA project. This report undertakes the hydrology assessment to feed into an appraisal based on a set of environmental outcomes which - along with physical screening of abstraction intakes to protect fish - aim for a flow regime that: attracts, maintains and improves passage for migrating salmon; maintains a temperature profile (and water quality) to support salmon spawning; maintains the habitats and species of the River Test SSSI, Lower Test Valley SSSI and Solent & Southampton Water Ramsar.
The assessment of licence change options shows that the option that meets all measurable the environmental outcomes propose the following:
reduce licence to 80 Ml/d from 136 Ml/d, reduce annual quantity to 29,200 Ml from 49,915 Ml, apply a flow condition of 390 Ml/d at Test Total from March through December and 355 Ml/d from January through February, and apply a flow condition of 265 Ml/d at Testwood Bridge from March thought December and 233 Ml/d from January through February.
Recent Actual quantities of abstraction are around 60 Ml/d and 21,700 Ml/year and so the ALS proposed licence conditions would not substantially change the normal operation of the licence but would meet the EFI flow regime which removes the risk of deterioration to the waterbody, and ensures supporting flow for migration of the SSSI salmon to change. Southern Water have also volunteered to reduce their annual to 30,000 Ml/year which is not far off from the ALS proposed quantity. When applying the salmon migration protection flow condition abstraction is restricted to zero in dry years (such as 2005-2006) for short periods of time.
The alternative management options of the Lower Test hydrological system all increase the low flows of the Great Test but do not mitigation the licence’s impacts on the Test Total flow, nor on the Great Test flows. The scenario flow results however, could be used alongside the licence quantity change to mitigate the impact of the salmon flow conditions on the available flow for abstraction and by delaying when proposed flow restrictions are employed.
Hydrology Assessment June 2017
References Atkins (2013), Lower River Test NEP - Volume 1 Report: October 2013, Atkins (for Southern Water Services) Environment Agency (2006), Test & Itchen Abstraction Licensing Strategy: Final Version March 2006, Environment Agency
Environment Agency (2007) Water Resource Standards for Freshwater Flows to Transitional Water Bodies: WFD 83, Final Report January 2007, Environment Agency
Environment Agency (2010a), Lower Test Project Baseline Data Report, v.2.0, February 2010, Environment Agency Environment Agency (2010b), Lower Test Project Flow Diversions Scoping Report, v.2.0, February 2010, Environment Agency Environment Agency (2013a), Test & Itchen Abstraction Licensing Strategy, Environment Agency, also found here https://www.gov.uk/government/publications/test-and-itchen- catchment-abstraction-licensing-strategy, [accessed 31/05/2017] Environment Agency (2013b), Lower Test Abstraction Licence Review - Scope Of Further Technical Work To Determine The Level Of Abstraction From The River Test That Is Environmentally Acceptable: November 2013, Environment Agency Environment Agency (2015), Setting a Hands Off Flow condition for total flows from the River Test into Southampton Water - Transposition of data from the River Avon (Hampshire) to the River Test (Draft), Environment Agency Environment Agency (2017), Invertebrate Ecological Assessment of Testwood Abstraction v8, Environment Agency Fewings, G.A. (2014), Salmon migration in the Great Test reach of the lower River Test, Hampshire – Determination of a salmon migration relevant river discharge threshold, Environment Agency Natural England (1971), Lower Test Valley SSSI Citation, https://necmsi.esdm.co.uk/PDFsForWeb/Citation/1001282.pdf, https://designatedsites.naturalengland.org.uk/SiteDetail.aspx?SiteCode=S1001282&SiteNa me=Test&countyCode=19&responsiblePerson=&SeaArea=&IFCAArea=, [accessed 31/05/2017]
WFD UKTAG (2008), UK Environmental Standard and Conditions (PHASE 1) Final report April 2008 (SR1-2006), WFD UKTAG, http://www.wfduk.org/sites/default/files/Media/Environmental%20standards/Environmental% 20standards%20phase%201_Finalv2_010408.pdf, [accessed 01/06/2017]