DOCSLIB.ORG

Recharge: the Key to Groundwater Pollution and Aquifer Vulnerability

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Recharge: the Key to Groundwater Pollution and Aquifer Vulnerability Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 Recharge: the key to groundwater pollution and aquifer vulnerability N. S. ROBINS British Geological Survey, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire, 03210 8BB, UK Abstract: Recharge is pivotal to understanding the processes by which groundwater pollu- tion can occur. It is implicit in the classification of aquifer units according to their vulnerabil- ity to pollution. The management of both groundwater resources and of individual groundwater sources cannot sensibly be undertaken without some knowledge of recharge: its quantity, its seasonality and, above all, the different routes through the sub-soil and the unsaturated zone by which it can occur. However, current estimates of recharge, other than on a research site basis, may be poor, both in the UK and overseas. This volume pro- vides a review of current research into these issues; this introductory paper attempts to high- light the thread throughout all of this work which collectively provides the basic information in support of the current and future management of groundwater resources and sources. This volume serves to highlight current develop- introductory paper attempts to highlight some ments in the assessment of groundwater pollu- of the issues pertaining to recharge estimation, tion, aquifer recharge and vulnerability, but and to the measurement and modelling of more particularly it illustrates the breadth of recharge; to the complex relationship between scientific enquiry that is currently being applied recharge, groundwater pollution and aquifer vul- to this complex, but topical, field of study. More- nerability; and to the importance of the recharge over, the volume demonstrates that the key to estimate. understanding many aspects of groundwater pol- lution lies alongside the reliable estimation of recharge, and also implicitly in the definition of Recharge estimation: the pitfalls aquifer vulnerability. To this end, a great deal of effort is now being put into investigating the Traditional estimates of recharge have depended processes that control recharge and to the appli- on the closure of the water balance for a given cation of contemporary findings. catchment or hydrogeological unit. Measure- Various groundwater management tools have ment of rainfall, evapotranspiration and run- been, and are being put into place by the Envir- off provides an indirect estimate of infiltration onment Agency in the UK. Many of these were by remainder. However, history has shown that first described in Policy and Practice for the Pro- each new method of determining infiltration tection of Groundwater (NRA 1992), a document and recharge based on secondary observations which has since been emulated by Scotland and (e.g. climatic and hydrological data) falls ulti- will shortly also be followed by Northern Ire- mately into part disfavour. land. This policy document clearly recognizes Calculation of evaporation from open water the important role of recharge and acknowledges using an evaporation pan, and the determination potential areas in which knowledge and data are of the same from meteorological data (Penman currently inadequate for the rigid application of 1948) was overtaken by the estimation of tran- the strategy. Data are least available in areas of spiration for particular types of vegetation upland Britain, including Scotland and Northern (Penman 1963). The general expression for tran- Ireland, where information has not been col- spiration depends on the sum of the available lected so assiduously by the developers of the energy and an aerodynamic term, the latter a lesser aquifers as it has been of necessity by work- function of wind-speed and humidity. Nowadays ers on the major aquifers such as the Chalk, the this technique, modified by Monteith (1965), Triassic sandstones and the Jurassic limestones forms the basis of the Morecs 40 by 40 km of England. Lack of detailed knowledge and block averages for the UK. In the absence of understanding, particularly of relevant pro- site-specific information, these are generally the cesses, is apparent from much of the work only available data. described in this volume; a great deal of research Estimates of run-off using low surface water has yet to be undertaken, on both a generic and a flow data (Gustard et al. 1992), although widely site-specific basis. available, provide little insight into the nature This volume concentrates on the key role of of the baseflow contribution that is actually recharge in groundwater management. This maintaining the low flow. They do, however, ROBINS, N. S. 1998. Recharge: the key to groundwater pollution and aquifer vulnerability. In: ROBINS,N. S. (ed.) Groundwater Pollution, Aquifer Recharge and Vulnerability. Geological Society, London, Special Publications, 130, 1-5 Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 2 N.S. ROBINS allow regional estimates of recharge to be made Environment Service of Northern Ireland. based on geolines for aquifers and non-aquifers, Besides, the role of till in inhibiting recharge is and low flow indices (Robins 1990). The hydrau- locally zero wherever it is removed or effectively lic relationship between surface and groundwater removed, for example in a quarry or a railway at any given point in a stream or river bed has cutting, or indeed where the source is below the first to be defined before low flow data can be protective cover, such as a leaking sewer set at used rationally. That being so, data are available the base of the till. The published vulnerability for large parts of the UK. maps identify 5 m as the critical thickness of till Even a simple parameter like rainfall is not as a protecting cover to an aquifer, but acknowl- easily assimilated into a recharge calculation. edge that till integrity is crucial but generally The rainfall event, its intensity and duration, unknown (Palmer et al. 1995). are as critical as the existing soil moisture The actual mechanism by which recharge status. Furthermore, microclimatic variation occurs is also very important. Price et al. (1993) may provide significant difficulties in rational argue that the Chalk has three sets of porosity: extrapolation of data even across a small catch- microfissures which allow rapid egress of storm ment area. Clearly, accurate determination of water; microfissures which promote storage and recharge must be done on a site-specific basis transport; and the intergranular matrix of the using a direct measurement such as a lysimeter Chalk blocks. Jones & Cooper (1998) demon- (see Jones & Cooper 1998) or using soil moisture strate that 30% of the potential recharge within measurement and event modelling (see Blackie et the Fleam Dyke lysimeter in Cambridgeshire al. 1998). These techniques are, however, expen- takes place within fractures. Many other aquifers sive. It may be that the way forward is through offer dual porosity, the Triassic sandstones are regional digital hydrogeological models which largely fractured and may also contain dilated will assist in establishing overall renewable bedding planes sufficient to offer rapid egress to resource values for a given aquifer unit rather percolating water. At the extreme end of the than point estimates of actual recharge. scale, karstic limestone provides selective, but A further significant problem arises in Britain potentially more rapid egress, transport and dis- through the existence of glacial till, which over- charge, in this case between sinks and risings, but lies bedrock over a significant part of upland with almost no storage (Daly & Warren 1998). Britain and much of lowland Britain north of The role of the soil zone is critical in the infil- the Severn and the Wash, and the Clay-with- tration process. The texture and grain size Flint that occurs on some of the Chalk outcrop. together control the ability of a soil to retain or It is often considered that the existence of till to drain soil moisture, both saturated and unsa- reduces potential recharge to an underlying aqui- turated. Palmer & Lewis (1998) explain in some fer by 30%, and such a rule of thumb has served, detail how the structure and density of a soil for the most part, reasonably satisfactorily. But influence the progress of permeating fluids, and what of the nature of the till itself?. There is a con- how the presence of clay minerals and organic siderable difference between the thick clay till matter influence the so-called leaching potential cover of the Fylde, and the often sandy till with of a soil (the ability of a soil to transmit non-con- pebble lenses that occurs in many areas else- servative pollutants). Cation exchange also where. The thick till deposits of North Yorkshire assists degradation and attenuation of some pol- and Humberside clearly inhibit all recharge, but lutants within the soil zone. how effective are the thin veneers of till and Estimation of recharge is, therefore, fraught Clay-with-Flint? with difficulty, a theme which is expanded by Mapping geologists have always concentrated Simmers (1998). Recharge can be measured on bedrock mapping; at best till is depicted as a directly and accurately on a site-specific basis, pale blue wash, with little regard for its integrity but extrapolation of such data, either in time at or thickness. Recent mapping of superficial the measured site or spatially away from the strata, such as that reported by Browne & measured site, is difficult, not least because the McMillan (1991) for the Glasgow area and else- prevailing conditions do not remain constant where in Scotland, has attempted to provide the and because the principal recharge mechanism detail with which recharge distribution can be may differ from one location to another. attempted, but areas so far covered are few. There is additional uncertainty in estimating For the most part, site-specific investigations recharge in a semi-arid climate where recharge are necessary in areas where low-conductivity events need not necessarily occur on an annual till is believed to be present.
Load more

Recommended publications
  • The Federal Role in Groundwater Supply
    The Federal Role in Groundwater Supply Updated May 22, 2020 Congressional Research Service https://crsreports.congress.gov R45259 The Federal Role in Groundwater Supply Summary Groundwater, the water in aquifers accessible by wells, is a critical component of the U.S. water supply. It is important for both domestic and agricultural water needs, among other uses. Nearly half of the nation’s population uses groundwater to meet daily needs; in 2015, about 149 million people (46% of the nation’s population) relied on groundwater for their domestic indoor and outdoor water supply. The greatest volume of groundwater used every day is for agriculture, specifically for irrigation. In 2015, irrigation accounted for 69% of the total fresh groundwater withdrawals in the United States. For that year, California pumped the most groundwater for irrigation, followed by Arkansas, Nebraska, Idaho, Texas, and Kansas, in that order. Groundwater also is used as a supply for mining, oil and gas development, industrial processes, livestock, and thermoelectric power, among other uses. Congress generally has deferred management of U.S. groundwater resources to the states, and there is little indication that this practice will change. Congress, various states, and other stakeholders recently have focused on the potential for using surface water to recharge aquifers and the ability to recover stored groundwater when needed. Some see aquifer recharge, storage, and recovery as a replacement or complement to surface water reservoirs, and there is interest in how federal agencies can support these efforts. In the congressional context, there is interest in the potential for federal policies to facilitate state, local, and private groundwater management efforts (e.g., management of federal reservoir releases to allow for groundwater recharge by local utilities).
    [Show full text]
  • Potential Groundwater Recharge for the State of Minnesota Using the Soil-Water-Balance Model, 1996–2010
    Prepared in cooperation with the Minnesota Pollution Control Agency Potential Groundwater Recharge for the State of Minnesota Using the Soil-Water-Balance Model, 1996–2010 Scientific Investigations Report 2015–5038 U.S. Department of the Interior U.S. Geological Survey Cover. Map showing mean annual potential recharge rates from 1996−2010 based on results from the Soil-Water-Balance model for Minnesota. Potential Groundwater Recharge for the State of Minnesota Using the Soil-Water- Balance Model, 1996–2010 By Erik A. Smith and Stephen M. Westenbroek Prepared in cooperation with the Minnesota Pollution Control Agency Scientific Investigations Report 2015–5038 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia: 2015 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Smith, E.A., and Westenbroek, S.M., 2015, Potential groundwater recharge for the State of Minnesota using the Soil-Water-Balance model, 1996–2010: U.S.
    [Show full text]
  • Law, Land Use, and Groundwater Recharge
    Stanford Law Review Volume 73 May 2021 ARTICLE Law, Land Use, and Groundwater Recharge Dave Owen* Abstract. Groundwater is one of the world’s most important natural resources, and its importance will increase as climate change continues and the human population grows. But groundwater management has traditionally been governed by lax and uneven legal regimes. To the extent those regimes exist, they tend to focus on the extraction of groundwater rather than the processes—referred to as groundwater recharge—through which water enters the subsurface. Yet groundwater recharge is crucially important to the maintenance of groundwater supplies, and it is also highly susceptible to human influences, particularly through our pervasive manipulation of land uses. This Article discusses the underdeveloped law of groundwater recharge. It explains why groundwater-recharge law, or the lack thereof, is important; it discusses existing legal doctrines that affect groundwater recharge, occasionally by design but usually inadvertently; and it explains how more intentional and effective systems of groundwater-recharge law can be constructed. It also sets forth criteria for judging when regulation of groundwater recharge will make sense, and it argues that a communitarian ethic, rather than the currently prevalent laissez-faire approaches, should underpin those regulatory approaches. Finally, it suggests using regulatory fees as a key (but not exclusive) instrument of groundwater-recharge regulation. * Harry D. Sunderland Professor of Law, University of California, Hastings College of the Law. I thank Lauren Marshall, Schuyler Schwartz, and Michael Kelley for research assistance and Michael Kiparsky, Nell Green Nylen, Jim Salzman, and participants at the University of Arizona environmental law works-in-progress conference and the Rocky Mountain Mineral Law Foundation water law works-in-progress conference for helpful suggestions at early stages and comments on drafts, and the editors of the Stanford Law Review for excellent editorial assistance.
    [Show full text]
  • Artificial Recharge of Groundwater Page 1 of 9
    Artificial Recharge of Groundwater Page 1 of 9 Artificial Recharge of Groundwater by Nayantara Nanda Kumar & Niranjan Aiyagari Fall, 1997 Table of Contents The increasing demand for water has increased awareness towards the use of artificial recharge to augment ground water supplies. Stated simply, artificial recharge is a process by which excess surface water is directed into the ground - either by spreading on the surface, by using recharge wells, or by altering natural conditions to increase infiltration -to replenish an aquifer. It refers to the movement of water through man-made systems from the surface of the earth to underground water-bearing strata where it may be stored for future use. Artificial recharge (sometimes called planned recharge) is a way to store water underground in times of water surplus to meet demand in times of shortage (NRC, 1994) Table of Conterits '~ethods of Artificial Rechar~e EWLRONMENTAL QUALITY COUNCIL September 1 1, 2006 h ttp ://ewr.cee.vt.edu/environmental/teach/gwprimer/recharge/rharge .htrnl ~xh~blt20 Artificial Recharge of Groundwater Page 2 of 9 -Direct - --Artificial- --- Rechar~e aspreading basics This method involves surface spreading of water in basins that are excavated in the existing terrain. For effective artificial recharge highly permeable soils are suitable and maintenance of a layer of water over the highly permeable soils is necessary. When direct discharge is practiced the amount of water entering the aquifer depends on three factors - the infiltration rate, the percolation rate, and the capacity for horizontal water movement. In a homogenous aquifer the infiltration rate is equal to the percolation rate.
    [Show full text]
  • Rainwater Management in Urban Areas
    water Editorial Rainwater Management in Urban Areas Brigitte Helmreich Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany; [email protected]; Tel.: +49-89-28913719 Abstract: Rising levels of impervious surfaces in densely populated cities and climate change-related weather extremes such as heavy rain events or long dry weather periods provide us with new challenges for sustainable stormwater management in urban areas. The Special Issue consists of nine articles and a review and focuses on a range of relevant issues: different aspects and findings of stormwater runoff quantity and quality, including strategies and techniques to mitigate the negative effects of such climate change impacts hydraulically, as well as lab-scale and long-term experience with pollutants from urban runoff and the efficiency of stormwater quality improvement devices (SQIDs) in removing them. Testing procedures and protocols for SQIDs are also considered. One paper analyses the clogging of porous media in the use of stormwater for managed aquifer recharge. The Special Issue demonstrates the importance and timeliness of the topic of sustainable rainwater management, especially with regard to growing cities and the challenges posed by climate change. Keywords: urban stormwater runoff; runoff pollution; sustainable urban drainage systems; evapotranspiration; managed aquifer recharge 1. Introduction Urbanization has led to the disruption or replacement of natural hydrological pro- cesses due to the sealing and degrading of natural soils. Typically, stormwater runoff from sealed urban surfaces is carried away by local sewer systems and discharged to surface Citation: Helmreich, B. Rainwater waters. However, this results in reduced evapotranspiration in urban areas, less cooling Management in Urban Areas.
    [Show full text]
  • Estimation of Groundwater Recharge Using Water Balance Coupled with Base-Flow-Record Estimation and Stable-Base-Flow Analysis
    Environ Geol (2006) 51: 73–82 DOI 10.1007/s00254-006-0305-2 ORIGINAL ARTICLE Cheng-Haw Lee Estimation of groundwater recharge using Wei-Ping Chen Ru-Huang Lee water balance coupled with base-flow-record estimation and stable-base-flow analysis Abstract In this paper, the long- complex hydrogeologic modeling or Received: 14 February 2006 Accepted: 12 April 2006 term mean annual groundwater re- detailed knowledge of soil charac- Published online: 11 May 2006 charge of Taiwan is estimated with teristics, vegetation cover, or land- Ó Springer-Verlag 2006 the help of a water-balance ap- use practices. Contours of the proach coupled with the base-flow- resulting long-term mean annual P, record estimation and stable-base- BFI, runoff, groundwater recharge, flow analysis. Long-term mean an- and recharge rates fields are well nual groundwater recharge was de- matched with the topographical rived by determining the product of distribution of Taiwan, which estimated long-term mean annual extends from mountain range runoff (the difference between pre- toward the alluvial plains of the C.-H. Lee (&) Æ W.-P. Chen Department of Resources Engineering, cipitation and evapotranspiration) island. The total groundwater National Cheng Kung University, and the base-flow index (BFI). The recharge of Taiwan obtained by the Tainan, Taiwan BFI was calculated from daily employed method is about 18 billion E-mail: [email protected] streamflow data obtained from tons per year. Tel.: +886-6-2757575 Fax: +886-6-2380421 streamflow gauging stations in Tai- wan. Mapping was achieved by Keywords Groundwater recharge Æ R.-H.
    [Show full text]
  • Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites
    EPA 510-R-15-001 Technical Guide For Addressing Petroleum Vapor Intrusion At Leaking Underground Storage Tank Sites U.S. Environmental Protection Agency Office of Underground Storage Tanks Washington, D.C. June 2015 Contents Recommendations .......................................................................................................................... 1 Background ................................................................................................................................. 1 Overview Of Petroleum Vapor Intrusion (PVI) ........................................................................... 2 Scope And Applicability .............................................................................................................. 3 Recommended Actions For Addressing PVI ............................................................................... 3 Supporting Technical Information ................................................................................................ 10 1. Petroleum Vapor Intrusion (PVI) ....................................................................................... 11 2. Typical PVI Scenarios ......................................................................................................... 33 3. Site Characterization And Conceptual Site Model (CSM) ................................................. 39 4. Lateral Inclusion Zone ....................................................................................................... 44 5. Vertical Separation Distance ............................................................................................
    [Show full text]
  • Chapter 33 Groundwater Recharge Chapter 33 Groundwater Recharge Part 631 National Engineering Handbook
    United States Department of Part 631 Agriculture National Engineering Handbook Natural Resources Conservation Service Chapter 33 Groundwater Recharge Chapter 33 Groundwater Recharge Part 631 National Engineering Handbook Issued January 2010 The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all pro- grams.) Persons with disabilities who require alternative means for commu- nication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, SW., Washington, DC 20250–9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. (210–VI–NEH, Amend. 34, January 2010) Preface The NRCS National Engineering Handbook (NEH), Part 631.33, Groundwa- ter Recharge, is derived from the following publication: • Technical Release No. 36, Ground Water Recharge, released by NRCS, June 1967 Note the following changes (canceled documents are replaced by the new documents): Canceled documents • NEH, Section 18, Ground Water (June 1978) • Technical Release No. 36, Ground-Water Recharge (June 1967) • NEH, Part 631, Chapter 33, Investigations for Ground Water Re- sources Development (November 1998) New documents NEH chapters in Part 631: • 631.30, Groundwater Hydrology and Geology • 631.31, Groundwater Investigations • 631.32, Well Design and Spring Development • 631.33, Groundwater Recharge (210–VI–NEH, Amend.
    [Show full text]
  • Hazards Induced by Groundwater Recharge Under Rapid Urbanisation
    HAZARDS INDUCED BY GROUNDWATER RECHARGE UNDER RAPID URBANISATION GROWTH OF water-supply provision value for unsewered city without mains drainage aximmainsum sewerage installation WATER IMPORTED M FROM DISTANT SOURCE Lima 1000 GROUNDWATER Merida FROM WASTE DISPOSAL WASTE WAST WATER-SUPPLY AND WATER-SUPPLY Potential urban PEPERIURBAN recharger WELLFIELDS 500 (from mains leakage,le Santa urban drainagedrainag and GROUNDWATER Cruz FROM CITY NUCLEUSwastewater disposal)dis shallow wells deeper boreholes 200 INITIAL SETTLEMENT URBAN EXPANSION Hat Yai Water obtained Water obtained from Urban aquiferaq Water obtained from:- from shallow city city boreholes and largely abandonedab (i) peri-urban wellfield 100 WATER wells. wells. in favour of SUPPLY SUPPLY periurban wellfields. (ii) imported water Pr Natural (non-urban)se environmentob w abl ere e m - incipient contaminationd -i nurbanim waterw table - water table declines 50 city um value of urban aquifer wit h stabilisesstabilise but for outside city (cannot urbanmain aquiferaq meet increased water - possible urban well contaminatedcontamis drainage demand). yield reductions None due to water table - urban water-table Deep infiltration (mm/a) 20 decline. rises IMPACTS IMPACTS Recharge resulting - incipient contamination of from urbanization peri-urban wellfields 10 (Pre-urban recharge nil) Non-urban recharge- over exploitation - excess pollution - over exploitation loading ICAL ES - excess pollution - excess recharge 5 None loading (local to city centre) 2000 1000 500 200 100 50 20 10 HYDRO- CAUSES - excess pollution GEOLOGICAL Rainfall (mm/a) loading between: between: between: - urban groundwater - urban water supply - peri-urban water-users HUMIDNone usersSEMI-ARID (private vs public) vs wastewaterARID (municipal, irrigation, disposal rural supply) - public supply - water supply vs POTENTIAL CONFLICTS (peri-urban) and wastewater irrigation disposal/re-use Q.4 - How do I assess the extent of urban groundwater use and the status of aquifer development? Lawrence AR, Morris BL and Foster SSD 1998.
    [Show full text]
  • Understanding of Groundwater Recharge for Sustainable Water Resource Management in Northern Victoria: a Review
    Understanding of groundwater recharge for sustainable water resource management in Northern Victoria: a review Project CMI Number: 104237 Author(s) Michael Adelana Department of Primary Industries Future Farming Systems Research Division, Cnr Midland Hwy/Taylor Street, Bendigo, Victoria, Australia © The State of Victoria, 2011 Disclaimer This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Acknowledgments Special thanks to Mark Reid for the efforts and time taken for the review of this report. The two consecutive reviews were thorough and his comments have greatly improved this report. Since this is one of the reviews and reports that he spent his last weeks of work with DPI on, I will like to dedicate the report entirely to his long years of profitable service ( 8, 397 working days ). “Mark thank you for being a source of encouragement to me since I joined the Department. I will not forget your selfless efforts and your encouraging words. Your retirement from DPI will leave a gap that may take a while to fill. All the best in your future endeavour.” ii Executive Summary Water resource management in the arid to semi-arid areas requires not only exploration and assessment of the available reserves, but also accurate determination of groundwater recharge in order to evaluate the sustainable yield of the resource.
    [Show full text]
  • Groundwater Recharge Gokce Sencan, Ellen Hanak
    FACT SHEET • AUGUST 2021 Alvar Escriva-Bou, Groundwater Recharge Gokce Sencan, Ellen Hanak Groundwater recharge is an important water management practice in California. ⊲ Recharge occurs when water seeps into the ground to replenish underground aquifers. Although some recharge happens incidentally—water flowing into the ground from rivers, unlined canals, or excess irrigation—intentional recharge can restore groundwater levels and store water for later use. ⊲ In coastal areas, intentional recharge prevents salty ocean water from entering freshwater aquifers. Recharge can also help prevent impacts from groundwater pumping, such as dry wells or sinking lands, while providing wetland habitat for birds, reducing flood risk, and storing water for droughts. ⊲ Active recharge is a longstanding practice in much of urban Southern California and parts of the Bay Area, Central Coast, and Central Valley. A variety of supply sources and methods are used to intentionally recharge aquifers. ⊲ Common methods include filling dedicated recharge basins or ponds, directing water to unlined canals and riverbeds, injecting water through wells, and using extra surface water (when available) to avoid pumping (“in-lieu recharge”). There is also growing interest in recharging aquifers by applying extra irrigation water to croplands, or by spreading water on fallowed fields and natural landscapes. ⊲ Supply sources include local floodwaters, surface water imported from other regions, and recycled water. Groundwater banks can make underground storage available for various parties. ⊲ While many local recharge projects do not track who benefits from the recharged water, groundwater banks recharge and store water on behalf of specific parties—both local and distant. These banks require formal accounting systems to keep track of balances, which decline during dry times as members withdraw water, and increase during wet times as water is deposited.
    [Show full text]
  • Stormwater Manual Volume 2 Chapter 2: Design Criteria
    Chapter 2 2 Design Criteria HAPTER This Chapter presents design criteria for sizing BMPs in the State of C New Hampshire to protect the state’s waters from the adverse impacts of development. Land development projects should employ site design and Best Management Practices (BMPs) to control peak runoff rates, provide stormwater quality treatment, use stormwater for groundwater recharge, and provide for stream channel protection. For projects that must comply with the AoT Regulations, specific parameters for sizing BMPs to meet these requirements are stipulated in the Env-Wq 1500. This Manual recommends these parameters for all development projects. This Chapter addresses the following design criteria for sizing stormwater management practices: ● Water Quality Volume (WQV) ● Water Quality Flow (WQF) ● Groundwater Recharge Volume (GRV) ● Effective Impervious Cover (EIC) ● Undisturbed Cover (UDC) ● Channel Protection (CP) ● Peak Control A summary of the requirements is included in Table 2-1, with detailed descriptions provided in the text that follows. In addition to these design criteria, other BMP-specific criteria also apply to the design of stormwater management practices. Those additional criteria are provided for each BMP in Chapter 4 – Designing Best Management Practices. Each of the criteria listed in Table 2-1 is further discussed below. Table 2-1. Summary of Design Criteria1 Design Description Criteria Water Quality WQV = (P)(Rv)(A) Volume P = 1” of rainfall (WQV) Rv = unitless runoff coefficient = Rv = 0.05 + 0.9(I) I = percent
    [Show full text]