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Figure 3.1 Main locations of karst-prone rocks in England and Wales (adapted from GeoSure information, British Geological Survey) 20 Science Report – Hydrogeological impact appraisal for groundwater abstractions
4 The HIA methodology 4.1 Overall HIA structure The HIA methodology is presented as a sequence of steps (Box 4.1), which should be followed for all groundwater licence applications. This may at first seem onerous, but the process has a logical progression, and the steps impose some discipline on each appraisal. At the same time, the steps in the process are not prescriptive, and the level of effort expended on each step can be matched to the situation. In other words, some steps will be a formality for many applications, but it is very important that the same thought-process occurs every time, to ensure consistency. In many cases, the process will be able to be streamlined. For example, it is recognised that the impacts of some groundwater abstractions are mitigated, by a proportion of the abstracted water being discharged back into the environment, for example. The HIA methodology assesses the impacts as if there were no mitigation, then adds back in the beneficial effects of mitigation. This is done because the locations and timing of the abstraction impacts may be different from the beneficial effects of the mitigation, and the mitigation measures may need to be optimised. Obviously, if all the abstracted water is consumed, and there are no mitigation measures, then Steps 5, 10 and 13 (see Box 4.1) can be omitted. The steps will now be considered in more detail. When following the procedure, the tiered approach described earlier should always be kept in mind, and the procedure repeated as many times as necessary (iterations within the tiers and moving through the tiers) until the required level of confidence has been achieved. Also, the basic principles established earlier (recharge makes no difference to impacts; impacts are the same upstream and downstream; and the abstraction spreads until it has stopped an equal amount of water leaving the aquifer) should be kept very much to the fore. Box 4.1: The HIA methodology Step 1: Establish the regional water resource status. Step 2: Develop a conceptual model for the abstraction and the surrounding area. Step 3: Based on the conceptual model, identify all potential water features which are susceptible to flow impacts. Step 4: Apportion the likely flow impacts to the water features, again based on the conceptual model. Step 5: For the relevant water features, allow for the mitigating effects of any discharges associated with the abstraction, to arrive at net flow impacts. Step 6: Assess the significance of the net flow impacts. Step 7: Define the search area for drawdown impacts. Step 8: Identify all the features within the search area which could potentially be impacted by drawdown. Step 9: For all these features, predict the likely drawdown impacts. Step 10: For the relevant water features, allow for the effects of any measures being taken to mitigate the drawdown impacts. Step 11: Assess the significance of the net drawdown impacts. Step 12: Assess the water quality impacts. Step 13: If necessary, redesign the mitigation measures to minimise the flow and drawdown impacts. Step 14: Develop a monitoring strategy, focussing on the features likely to experience flow or drawdown impacts. Science Report – Hydrogeological impact appraisal for groundwater abstractions 21
Page 1 and 2: Hydrogeological impact appraisal fo
Page 3 and 4: Science at the Environment Agency S
Page 5 and 6: Contents 1 Introduction 1 1.1 Purpo
Page 7 and 8: 1 Introduction 1.1 Purpose of this
Page 9 and 10: vi. Licence application and determi
Page 11 and 12: systems, this could be the variatio
Page 13 and 14: simplify the mathematical represent
Page 15 and 16: Figure 2.2 Tiered approach to conce
Page 17 and 18: harder to visualise, but include in
Page 19 and 20: even this assumption cannot be take
Page 21 and 22: significant. Impacts at a regional
Page 23 and 24: of the equations are only relevant
Page 25: etween the release point and a samp
Page 29 and 30: Table 4.1 HIA in relation to CAMS a
Page 31 and 32: equilibrium? This step is basically
Page 33 and 34: Wetland B and a stretch of River B,
Page 35 and 36: • If the discharge is into a stre
Page 37 and 38: Take the sketch map from Steps 3 an
Page 39 and 40: The proposed abstraction rate (Q) i
Page 41 and 42: considering drawdowns separately, t
Page 43 and 44: • The impact may have to be judge
Page 45 and 46: unsaturated zone may change as well
Page 47 and 48: (1984), who also noted that pulling
Page 49 and 50: 4.3.2 Reducing the uncertainty At t
Page 51 and 52: that have been identified during th
Page 53 and 54: include a picture or diagram of eac
Page 55 and 56: References Acreman M C (2004). Impa
Page 57 and 58: Price M (1996). Introducing Groundw
Page 59 and 60: Glossary Abstraction: Removal of wa
Page 61 and 62: Appendix 1: Regulatory context Intr
Page 63 and 64: Sites of Special Scientific Interes
Page 65 and 66: Test 5 (optional local tests): allo
Page 67 and 68: Appendix 2: Test pumping Introducti
Page 69 and 70: the nature of the pumping test; a m
Page 71 and 72: References Brassington R (1998). Fi
Page 73 and 74: Karst groundwater systems Karst gro
Page 75 and 76: location and topology of the condui
Page 77 and 78:
Group 4 represents aquifers with di
Page 79 and 80:
Step K2: Develop a conceptual model
Page 81 and 82:
with much higher frequency is of co
Page 83 and 84:
ivariate linear least squares regre
Page 85 and 86:
References Atkinson T C (1977). Dif
Page 87 and 88:
Appendix 4: Crystalline rock Introd
Page 89 and 90:
Ta 0. 4 K b = = = 0.008 m/d D 51 Li
Page 91:
References Banks D (1992). Estimati
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