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5 Monitoring 5.1 Purpose of monitoring The subject of monitoring has been mentioned briefly several times already in this report, but will now be discussed in much more detail. This chapter is by no means an exhaustive treatment of the subject, but serves to highlight the main issues of relevance to <strong>HIA</strong>. The focus of this section is on monitoring water levels and flows, but monitoring can also include water quality sampling and ecological surveys. In the context of groundwater abstraction, the main purposes of monitoring are as follows: • To establish the baseline environmental conditions before the commencement of abstraction. • To fill gaps in the knowledge of the hydrogeology and hydrology of the area around an abstraction. In other words, to improve the conceptual model by reducing the uncertainty. • To demonstrate compliance with conditions attached to relevant abstraction licences or discharge consents. • To trigger mitigation measures or temporary cessation of abstraction, if the water level in a receptor (such as a wetland) falls below an agreed trigger level, for example. • To provide early warning of adverse impacts on receptors such as sensitive water-dependent ecosystems, or other abstractions. • To accumulate data during the lifetime of a time-limited licence that can be used when the time comes to review the licence. 5.2 Principles of monitoring In some cases, monitoring data are collected haphazardly, without any clear idea of why certain types of data are being collected. Again in the context of groundwater abstraction, the main principles of monitoring are as follows: • The overall objectives of the monitoring system should be clearly defined. There will probably be more than one objective, and these are likely to be related to the main purposes described above. It is a good discipline to write these objectives down, if only to focus the mind on what the monitoring system is trying to achieve. • The design of the monitoring system should be based on a good conceptual model. Having said that, it may of course be that there is significant uncertainty about the conceptual model, which the monitoring is trying to address. The design should therefore be based on the best current understanding of the conceptual model, with the design reviewed and the system adapted as understanding increases. • The design of the monitoring system should be risk-based, that is, the burden of monitoring effort should be reasonable and appropriate for the environmental risks associated with the abstraction in question. One way to achieve this is to focus the monitoring on the water-dependent features 44 Science Report – Hydrogeological impact appraisal for groundwater abstractions
that have been identified during the <strong>HIA</strong> as being potentially impacted by the abstraction. Again, it is useful to write down an explicit description of why the monitoring system is designed in a certain way. • There should be a clear idea of what the function of each individual monitoring point is, so that all parties are clear why a specific type of data is being collected, and what are the specific issues of concern. This can easily be forgotten over time if not written down, especially as personnel often change within the lifetime of a monitoring system. • The construction of each monitoring point should be appropriate for its function. For example, for monitoring water levels in a wetland, it would be no good using a deep borehole that is not hydraulically connected to the wetland itself. • The same thought should go into deciding at what frequency the data should be collected, and the system reviewed periodically. It may very well be that money can be saved by reducing monitoring frequency once an understanding has been gained of the variability of the parameter being measured. In other words, there may be little point in collecting daily readings from a borehole in a Triassic sandstone aquifer (where water levels tend to vary slowly, due to the high storage). Conversely, once-daily measurements of flow in a ‘flashy’ stream might be far too few, as flow peaks due to quick run-off from storm events might be missed completely. In karst aquifers, the monitoring frequency should be high Gauging stream flows because of the rapid response. • Stringent quality control procedures are necessary to ensure that monitoring data are of satisfactory quality. Such procedures should include the routine calibration of measuring instrumentation, the routine manual checking of automated instrumentation, the routine screening of data for both instrumental malfunction and operator errors, and the documentation of all of the above procedures. It is also essential to safeguard the continuity of monitoring, and to retain and archive all monitoring data systematically (including the quality control procedures themselves). The value of writing down the objectives and the thinking behind the design of the monitoring system has already been emphasised. It is good practice to include these in a written Monitoring Plan, which should cover the following subjects (as a minimum): i. The overall objectives of the monitoring system. ii. The reasoning behind the design of the monitoring system, relating the design to specific water-dependent features that are at risk. iii. The function of each individual monitoring point. iv. Construction details of each monitoring point, including drawing and photographs. v. Health and safety risk assessment for each monitoring point. Science Report – Hydrogeological impact appraisal for groundwater abstractions 45
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 and 26: etween the release point and a samp
Page 27 and 28: 4 The HIA methodology 4.1 Overall H
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: 4.3.2 Reducing the uncertainty At t
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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