sign in sign up
<<
Home , Groundwater pollution

International Association of Hydrogeologists Strategic Overview Series ECOSYSTEM CONSERVATION &

KEY MESSAGES What are groundwater-dependent ecosystems and why are they important ?

• groundwater-dependent ecosystems A groundwater-dependent ecosystem (GDE) is a community (GDEs) comprise a complex subset of micro-organisms, animals and , and associated of ecosystems of major significance substrates, whose functioning relies on the presence of in the conservation of - under the ground and/or its emergence to the surface. including many vital sites covered by the RAMSAR Convention and many Some GDEs are supported entirely by groundwater while others that remain unprotected others also receive water from different sources, but the groundwater contribution is critical as regards water • GDEs have direct value for the human chemistry to nourish certain species, and provide stable population from fish and water temperature and absence of sediment load. production, water storage and purification, and indirect value in terms of and/or habitat GDEs are mainly -surface features of various types : • aquatic – including springheads, and those wetlands, • there is need to identify GDEs under streams, rivers and lakes receiving groundwater three main types – aquatic, terrestrial, discharge (which are the main focus of attention here) subterranean – and improve • terrestrial – with phreatophyte vegetation, either shallow- understanding of their relationship rooted in alluvial settings (such as some lowland with the physical and chemical status and meadows) or deep-rooted in arid zones with much of groundwater deeper water-table. • degradation of GDEs can occur But they can also be subterranean – notably in limestone because of anthropogenic formations with karstic caverns and fissures inhabited by modifications to flow regimes small invertebrates and some specialised vertebrate species. and salinisation or of their groundwater

EL ROCIO WETLAND IN THE DOÑANA • potentially negative impacts on the NATIONAL PARK OF SOUTHERN SPAIN functioning of GDEs from groundwater withdrawals for irrigated or urban water-supply need to be assessed and managed

• modest increases in groundwater salinity and/or pollution (with nutrients and ) can drastically impact ecosystem structure and cause extermination of key species

This Series is designed both to inform professionals in other sectors of key interactions with groundwater and hydrogeological science, and to guide IAH members in their outreach to related sectors.

WETLAND ECOSYSTEM IN ARID REGION FROM RAMSAR SITES TO KNOWING YOUR WITH ONLY LIMITED CONTEMPORY GROUNDWATER LOCAL SPRINGS REPLENISHMENT AND FOSSIL AQUIFER FLOW The RAMSAR Convention (named after the town in Iran springs where it was signed in 1971) constitutes an agreement by and 169 countries to take action on the conservation of priority oasis wetlands (aquatic ecosystems many being GDEs), in the special interest of protecting wildfowl habitats. The agree- ment currently involves over 2,200 sites amounting to a land area in excess of 210,000 km2. At a very different scale, the ‘Conoce Tus Fuentes’ (‘Know Your Springs’) web-based AQUIFER initiative of the Andalucian Government of Spain has suc- ceeded in mobilising the general public, under academic coordination, in primary mapping of 10,100 springs across this relatively arid region. Both are excellent examples of approaches to raising political and public awareness of GDEs.

AQUATIC STREAMBED ECOSYSTEM IN HUMID REGION ALONG UPPER REACHES OF RIVER FED BY PERENNIAL AND INTERMITTENT GROUNDWATER DISCHARGES GDEs are fundamental to the conservation of biodiversity – many being vital for survival of a intermittent wide variety of species and figuring prominently stream h perennial in sites covered by the RAMSAR Convention. ighest w stream ater- tabl zone of e Moreover, GDEs can be of significance as a fluctuation renewable source of human nutrition and as key lo west AQUIFER wate r-table features in the local landscape such as springs and lagoons.

Some prefer to introduce the term ’aquifer- dependent ecosystem’ to emphasise that COASTAL LAGOON ECOSYSTEM DEPENDENT UPON SLIGHTLY BRACKISH WATER constrain the groundwater flow on which GENERATED BY MIXING OF FRESH GROUNDWATER AND ecosystems depend. It should also be noted that LIMITED SEAWATER INCURSION some aquatic ecosystems occur in aquifer recharge zones and represent a major source of groundwater system replenishment.

lagoon sea

AQUIFER How can degradation of groundwater- dependent ecosystems arise? saline/groundwater interface The degradation of GDEs occurs as a consequence of both modification of natural groundwater flow TERRESTRIAL SAVANNA ECOSYSTEM regimes and salinisation or pollution of groundwater. DEPENDENT UPON EXCEPTIONALLY DEEP-ROOTED TREES AND BUSHES TAPPING THE IN ARID REGION All groundwater pumping has some effect on deep-rooted savanna trees water-table levels – but in terms of ecosystem calcrete lenses impact the main concern is where the cumulative effect of major extraction (for agricultural

AQUIFER or urban water-supply) causes substantial and per- very limited lateral groundwater flo sistent water-table lowering. This can also sometimes w arise in the absence of intensive groundwater use:

2 POTENTIAL INTERFERENCE WITH GDEs OF GROUND- WATER PUMPING FROM A MULTI-LAYERED AQUIFER deep waterwells mainly shallow waterwells with potential impact on with probable impact on wetland ecosystem 2 wetland ecosystems 1a/1b

1a 1b 2

lens

AQUIFER

1a 1b 2 wetland ecosystems

• if recharge zones experience major changes from depth in aquifers (or contained in aquitards), that increase consumptive water-use (eg : low- which are then further concentrated in irrigated land afforestation) or riverbed modifications before to shallow groundwater. that decrease aquifer replenishment (eg : impermeabilisation or diversion) Groundwater pollution can have a similar impact • where dewatering for tunnel construction – and the most widespread cause is agrochemical or operations seriously impacts the leaching from land-use practices. Pesticides and groundwater flow regime. nutrients that are leached from soils eventually The resulting reduction in groundwater discharge reach the water-table, and can migrate to GDEs can trigger a change in ecosystem functioning in natural discharge zones. The effect of ground- and in turn ecosystem structure, and in extreme deterioration, notably increases of cases cause its complete elimination. nitrate, ammonium or (even at low concentrations) and/or trace contamina- There is often uncertainty about the reaction of tion, may to greater ecosystem impacts than individual species to hydrological change and groundwater flow diminution. Elevated nitrate species interdependence within a GDE. More- and phosphate concentrations can cause over, the way that groundwater discharges into, ecosystem , eliminating oxygen and interacts with, the surface environment and killing fish and small aquatic animals. (in the transitional hyporheic zone) can be critical to aquatic (not just the presence of water). Whilst certain irreversible changes can What can be done to protect groundwater- occur in relatively short periods (such as dependent ecosystems? oxidation of wetland or streambed sediments), some species are adapted to survive hydro- Two main lines of action are required for protect- logic extremes, and those naturally exposed to ion of GDEs and have been strongly advocated for variations in groundwater behaviour (for example all sites covered by the RAMSAR Convention: in ephemeral streams) are more resilient. • increasing knowledge of their hydrogeo- logical and ecological condition, and the Modest increases in groundwater salinity can economic consequences of degradation for change ecosystem structure dramatically, and human well-being cause extermination of some species. This can • integrating their protection into basin/aquifer occur where irrigation waterwells mobilise salts water- and land-use management.

3 Systematic assessment is required for each GDE to groundwater system. Economic assessment of understand its evolving relationship with underly- GDEs will require clear definition of the benefits ing aquifers, to evaluate groundwater quality and of these ecosystem services including : define chemical baseline, to identify anthropo- • direct values to the human population in genic pressure trends, and to determine the terms of fish and plant production, and socioeconomic contribution of ecosystem services. providing water storage and purification The end product should be a conceptual model of • indirect values from sustaining biodiversity, GDE functioning, using GIS and other data habitat and landscape for social, cultural, management systems to display results clearly. aesthetic and ethical reasons. But in the developing nation context it is recog- All measures that strengthen the governance and nised that direct use values from harvested plants practical management of groundwater can con- and animals, and from or habitats for tribute, or be adapted, to the cause of protecting tourism are likely to be more important. If the GDEs – by including criteria to maintain ground- livelihoods of poor and vulnerable people depend water levels and conserve groundwater qual- directly on the functioning of GDE’s there is a ity to meet the requirements of the ecosystem risk that ecosystem value may be systematically receptor. This will often imply greater constraints under-estimated. on the volume and distribution of groundwater withdrawals than would otherwise have been Disputes are often likely to arise over the necessary, together with more severe controls balance between improving rural livelihoods and over groundwater contaminant load than needed sustaining healthy ecosystems. Decision-making to conserve drinking-water quality. A balance needs to be informed by sound technical and between improving rural livelihoods and sustain- economic analysis, and it is thus important to ing ecosystem health needs to be achieved. incorporate economic evaluation into the analy- sis. A useful framework for GDE valuation, and However, social development pressures may be the relationship between human wellbeing and such as to prevent control of groundwater levels ecosystems, is the so-called ‘ecosystem services and quality in an entire aquifer system in the approach’ of the UN Millennium Ecosystems interest of GDE conservation, and alternatives Assessment Project. It argues that human progress may need to be pursued such as: has always relied on natural resources and • acting selectively to introduce ‘protection functioning ecosystems. The assessment must use zones’ around GDEs, capable of assuring reliable historic data and scientific studies. shallow groundwater quality and reducing The method also includes assessment of the groundwater level interference impact (observed and forecast) of a set of ‘driver • artificial recharge to supplement groundwater factors’ that change GDE behaviour. flows and improve quality over limited areas in the interest of GDE conservation, or even SALAMANDER SPECIES ENDEMIC TO A pumped compensation flows when aquifer SINGLE SPRING OF THE TEXAS levels fall below some critical level.

How can the value of groundwater- dependent ecosystems be assessed?

GDE functions are an important component of overall environmental services provided by a

4 KARST GROUNDWATER ECOSYSTEM AND CROATIAN EXAMPLE OF SPRING DISCHARGE

SWALLOW HOLE RECHARGE AREA

COVER DEPOSITS sinking stream epikarst well UNSATURATED ZONE spring

SATURATED ZONE

An economic analysis for this purpose will ecosystems. As such it is critical that GDEs are normally entail a relative assessment of the : identified, located, characterised and inventor- • cost of protection in terms of the loss of alter- ised – including designation of GDEs of major native uses of groundwater and land, and the importance, such as those covered by the administration of the land-use and ground- RAMSAR Convention. water control policy • benefits of protection in terms of in-situ value An appraisal of GDE vulnerability with respect to of groundwater and groundwater-related potential impact from land development and re- ecosystem services. source withdrawal is a critical aspect of the assess- In this context an analysis based on marginal ment. Appropriate legal provision and institutional cost-benefit is likely to better reflect the arrangements will be required to implement the situation on-the-ground, and scenarios of partial required GDE protection. protection (as opposed to total protection) of GDEs will also need to be considered. In developing countries, strong social pressures are likely to arise for further agricultural and urban development, which are likely to impact What institutional and legal arrangements GDEs either directly (through increased ground- can facilitate consideration and protection water withdrawals) or indirectly (through in- of groundwater environmental functions? creased groundwater contaminant load). Thus an important issue in relation to the implementation Policies need to be elaborated and implemented of groundwater management is which stake- through interaction between national and local holder should represent the interests of a given environment agencies based on the following ecosystem. There are a number of possiblities: principles : • an NGO representing the local community • GDEs have important and diverse value for dependent on a healthy ecosystem or gener- human wellbeing ally interested in ecosystem conservation • groundwater use should be managed so as to • the local land authority representing the give priority to protecting GDEs balance of interests of all land-owners • land-use planning and development should • an environmental agency at national or local aim to minimise impacts on GDEs. territorial level. Without the existence of a groundwater use There is a major need to promote public aware- rights system and the participation of a clearly- ness of the groundwater-dependence of many identified stakeholder group, it is unlikely that

5 International Association of Hydrogeologists Strategic Overviews Series ECOSYSTEM CONSERVATION & GROUNDWATER

the interests of GDE sustainability will get an adequate hearing PRIORITY ACTIONS in the discussion of land and water development options. • foster social awareness of the Given the likelihood of significant uncertainty over the precise importance of groundwater for level of impacts on GDEs arising from a given water-resource sustaining viable ecosystems – and mobilise appropriate stakeholders for and/or land-development proposal, the regulatory agency gen- GDEs (such as conservation NGOs and erally needs to adopt a clear decision-making strategy. This will local land authorities) normally have to embrace one or other of the following : • the of not authorising developments • increase knowledge of hydrogeological until ecosystem risks are established and managed (which and ecological conditions of GDEs and may be too conservative for most developing countries) the economic consequence of their degradation for human well-being • pragmatic initial groundwater resource development, with

careful monitoring, evaluation and adaptation of plans in • include GDE conservation within the event of significant impact integrated catchment management or • reserving specific environmental flow or conserving water- at least act selectively to incorporate table level within the overall groundwater resource manage- GDE protection zones into ment strategy and planning to sustain key wetlands. groundwater resource use and land-use control policy

The complexity of estimating the impacts of groundwater • adopt an extraction and pollution make it difficult to define limits that can approach to conserving GDEs, be readily measured and legally enforced – but legislation can informed by careful monitoring and provide for this by stipulating that ‘in cases where stakeholders assessment, given the likelihood of do not agree with the regulatory authority’s determination they significant uncertainty in predicting can undertake more detailed studies at their own cost’ ecosystem impacts

• consider augmentation of ground- SELECTED BIBLIOGRAPHY water inflows to aquatic ecosystems if • Colvin C et al 2007 Aquifer-dependent ecosystems in key hydrogeologic typesettings of South Africa, Water Research Commission Report WRC-TT-301-07 (Pretoria). the water-table should fall below a • Klove B et al 2011 Groundwater Dependent Ecosystems - (1) hydrogeological status and defined critical level due to abstraction trends (2) ecosystem services and management under risk of climate change and land-use or drought intensification. Environmental Science & Policy 14: 770-793. • Kreamer D et al 2015 Groundwater Dependent Ecosystems – science, challenges and policy directions. Nova Science -Groundwater 205-230 (). • Mahler B J & Bourgeais R 2013 Dissolved oxygen fluctuations in karst springflow with implications for endemic species : Edwards Aquifer, Texas, USA. J 505:291-298 • Manzano M et al 2005 Effects of localised intensive aquifer exploitation on the Doñana wetlands (SW Spain). IAH Selected Papers 7 : 209 – 219. • Murray B et al 2006 Valuation of groundwater-dependent ecosystems: a functional methodology incorporating ecosystem services, Australian Journal of Botany 26 : 221-229. • RAMSAR 2010 Managing Groundwater – guidelines for the management of groundwater to maintain wetland ecological character. Ramsar Wetlands Handbook 11. IUCN Ramsar Convention Secretariat (Gland-Switzerland) www.ramsar.org/sites/default/files/documents . • US-EPA 2012 Identifying and protecting healthy watersheds : concepts, assessments and management approaches US Environmental Protection Agency 841-B-11-002 (Washington DC). • WRI 2005 Millennium Ecosystem Assessment – ecosystems and human well-being – wetlands and water synthesis. World Resources Institute (Washington DC) www.millenniumassessment.org/documents.

COORDINATION : Stephen Foster & Gillian Tyson CONTRIBUTIONS : Christine Colvin, Mike Wireman, Marisol Manzano, Dave Kreamer, Nico Goldscheider & Catherine Coxon IAH 2016 MANAGEMENT : Bruce Misstear & John Chilton www.iah.org