Management of aquifer recharge and discharge processes and aquifer storage equilibrium

Transcription

1 A Global Framework for Action GEF-FAO Governance Project A Global Framework for Country Action Digest 1 of Thematic Paper 4: Management of aquifer recharge and discharge processes and aquifer storage equilibrium This is a précis of the findings of this 53p thematic paper prepared on behalf of IAH in 2012 for regional consultation meetings on this project. The document also describes 11 case studies. Relevance of managing aquifer recharge, discharge and storage equilibrium for groundwater governance Sustaining storage within aquifers is important for supporting groundwater dependent ecosystems and surface water resources, food production, drinking water supplies and groundwater-dependent economies. The absence of effective controls has led to widespread serious declines in aquifer storage. In almost all groundwater basins, groundwater depletion will become inevitable due to strong economic drivers for use, population growth, improved efficiency of groundwater extraction, and in some areas, a drying climate. Effective governance arrangements are vital for equitable groundwater sharing among the current population and with future generations. This will require a quantitative understanding of groundwater systems, informed communities and effective regulation of groundwater use. However, Thematic Paper 4, gives ample evidence in many locations of good governance being effective in restoring depleted aquifers. Three tools for effective groundwater governance were identified; management of discharge, management of recharge and substituting alternative water sources (conjunctive use). These tools were used alone or in combination to effectively manage groundwater storage. Community engagement was important in all cases, and in some cases, local reforms were successful without reliance on state or national supporting policies. However national policies and frameworks would help make good governance ubiquitous. Figure 1. An aquifer can be brought into hydrologic equilibrium by either reducing extraction, or augmenting supplies, either through groundwater replenishment or providing alternative supplies. Use Initial Situation deficit in over-exploited aquifer supply-able without excessive adverse impacts Management interventions Demand Management Alternative supplies MAR to replenish aquifer Final situation used without excessive adverse impacts 1

2 GEF-FAO Governance Project - Digest of Thematic Paper 4 Coverage: main aspects and dimensions This scope of Thematic Paper 4 paper is global, covering case studies in countries in different continents, climatic zones and stages of development, and in rural and urban areas. It looks at the importance of each of the three tools used alone and in combination. While stressing the primacy of demand management, it gives particular emphasis to managing aquifer recharge, because this is an under-used tool among water resources managers even though it can be more economic than the more strenuous demand management measures. It can also be used as a lever to assist demand management, for example by pricing water to cover sufficient replenishment that gives groundwater users a beneficial return for their costs while also encouraging efficient use. Surface waters, such as streams and lakes, urban stormwater, treated sewage effluent and desalinated seawater, can be recharged directly to aquifers or be a substitute for groundwater supplies (ie conjunctive use). Hence in temperate, semi-arid and even arid areas, where there is intermittent availability of any suitable source of surface water, managing recharge can be an effective part of groundwater governance. In arid areas with no alternative supplies, mining of groundwater needs careful management of water use to prolong the resource, increase its value, and plan for orderly closure of the resource. Table 1. List of case studies, management instruments employed and their effectiveness Case study Demand management Managed aquifer recharge Alternative supplies Effectiveness Ilocos Norte, Philippines Farmer led yes Andhra Pradesh, India farmer led localised yes Maharashtra, India ban on tube wells and sugar cane strategic yes Castilla y Leon, Spain user collective failed to curb use basins treated wastewater no Namoi Valley, Australia Entitlements issued river water (also licensed) yes Kitui, Kenya sand dams yes Coastal Bangladesh recharge wells yet to be assessed Mancha Occidental, Spain recharge wells Guadiana channel yet to be assessed Bangkok, Thailand Pricing to curb demand treated surface water yes Alice Springs, Australia Entitlements and use efficiency measures minor soil aquifer treatment yes for adopted objective Arizona, USA rights assigned water banking CAP and treated wastewater yes 2

3 Insight into constraints/ issues and limitations Given that even chronic long-term groundwater depletion is a problem that has proven to be overcome by effective local groundwater governance, why are these demonstrated effective methods not in widespread use? a) Prevailing unambiguous evidence is that having groundwater entitlements based on land-ownership, enshrined in law, fails to recognise the public good nature of groundwater and its essential role in sustaining streams, lakes, wetlands and ecosystems and fails to sustain storage. The concept of a groundwater system being divided into fenced parcels with independent ownership is as absurd as the notion that a landholder would own migratory birds that rested on their property. Information and legislative reform is necessary to empower effective water resources management. b) A quantitative understanding of groundwater systems is necessary to define the allocatable pool. Very often there is little monitoring and recording of groundwater levels, and groundwater use is poorly quantified. These measures are necessary to provide assurance that groundwater users are equitably reducing their demand. c) In some communities, groundwater users see themselves as competitors for the resource and need external intervention to help build social capability for collective action. d) Policies and institutions that provide drivers for water conservation and replenishment are lacking. e) In general there is an awareness of managed aquifer recharge (MAR) among some water users but rarely among water resource managers, and hence a failure to appreciate its complementary role with demand management in sustaining groundwater systems and drought relief. Policies that gain maximum advantage from MAR, identified in TP4, are only emergent and just starting to be adopted in some jurisdictions. f) Technical capabilities for managed aquifer recharge (site selection, design, construction, operation, maintenance, water quality management) are rarely available within many areas where this suite of techniques would be valuable and economic. g) There was very sparse information available on case studies of the management of fossil groundwater resources. However one case study was reported. Key things that decision makers / wider engaged public need to know Firstly, good groundwater governance is capable of meeting the objectives of maximizing the utility of aquifers while sustaining the environment and providing security for meeting human needs. Many areas where groundwater is a dominant irrigation resource or the main supply for cities are water-stressed and these objectives are not being achieved. However, in a number of reported local initiatives with public engagement these objectives have been met and deteriorating storages replenished. Best management practice involves quantification of the water resources and formation of plans that account for all resources, groundwater and surface water, including recycling of stormwater and treated sewage effluent where relevant. If groundwater is not over-allocated, it is easier to manage through a user collective, or to build social capacity for collective action so that this can be formed and manage the resource with technical support from government. Good examples of farmer-led groundwater management are reported in Ilocos Norte, Philippines and in Andhra Pradesh, India. 3

4 GEF-FAO Governance Project - Digest of Thematic Paper 4 Where groundwater is over-allocated, and other water resources are available, demand management can be complemented with managed aquifer recharge or alternative sources of water supplied directly (conjunctive use). Implementation of these will require policies and regulations that entrust consultation and establishment of a groundwater allocation plan or sharing agreement with an entity charged with managing the groundwater resource. Transferable entitlements for recharge credits are defined in TP4. A groundwater allocation plan should be based on a scientific defensible assessment of the available yield of the aquifer and shares in that yield determined for all existing users. No new users would be allowed. The volumetric allocations would be set periodically, say each 5 years, and any trend in groundwater storage over that interval would be used to revise the allocation for the following period. Allocations should be tradable to allow new entries through purchase of existing allocations. If groundwater is over-allocated and there are no other water sources available, a groundwater allocation plan would involve demand management, and the primary goal would be to maximize the utility and to prolong the life of the remaining resource through water conservation measures. An exit strategy is warranted and this should be communicated well in advance to avoid wasted investment. as a distributed resource requires participation in management by the stakeholder community. Introducing measurements, such as groundwater level and electrical conductivity, flow meter or area of each crop type, rainfall and evaporation, and crop yields would help communicate the link between groundwater system health and the overlying land and water uses. Most significant prospects and recommendations governance reform in many jurisdictions is warranted. Current unlimited entitlements based on land ownership defy the laws of nature. Inequitable and unachievable entitlements that are currently enshrined in law need to be revised. A new system of entitlements is warranted, based on scientifically defensible methods. Internationally applicable principles for formation of such entitlements are laid out in Thematic Paper 4. resources assessment needs to be quantitative to identify the volumetric allocation from each aquifer, or allocations from different components of each aquifer. In order to pragmatically implement allocations in depleting aquifers, it may be necessary to provide supplementary, temporary, reducing, nontradable allocations to groundwater users to allow time for adjustment. Allocations will need to be periodically reset, (eg say each 5 years) based on monitoring of groundwater levels and groundwater use. For example if in parts of the aquifer there is a trend of storage decline then in that area groundwater users would recognize the need for reducing allocations. TP4 identifies at least 10 different forms of demand management methods. Water resources assessments need to examine all water resources, not just groundwater alone. This will identify opportunities for managed aquifer recharge to replenish aquifers with surface water at times when surface water is allocatable, taking account of environmental flow requirements. Alternatively or additionally, surface waters may be harvested and distributed to replace groundwater use, that is, conjunctive use. 4

5 Successful management often involves two or three of these elements, with demand management being the highest priority. Increasing recharge or use of surface water sources are unlikely to be successful in restoring groundwater levels unless demand management is also superimposed. A hierarchy of options can be identified based on the relative unit cost of the loss of production from demand reduction, and of implementing managed aquifer recharge or an alternative supply. Policies that encourage conservation and replenishment of groundwater may be developed that would give greater impetus for private investment in these. For example in Arizona, a water bank has been established and developers of new urban subdivisions need to provide 100 years water supply. They do this by going to the water bank to fund the best value project proposed in their area. This will generally consist of a groundwater recharge project using either Central Arizona Project water or local recycled wastewater. In irrigation areas, groundwater users groups may jointly fund the cost of a managed aquifer recharge project in order to avoid a further decline in groundwater allocations. Capacity building for managed aquifer recharge in much of south and east Asia is limited. Unless water resources managers identify opportunities for managed aquifer recharge and they have access to local technical skills to implement and maintain managed aquifer recharge projects, this prospect for maintaining production at minimum cost cannot be realized. It is recommended that organizations supporting groundwater development and protection, invest in skills development among government and non-government organizations so that managed aquifer recharge projects may be used to sustain groundwater systems. MAR-NET a UNESCO-IAH initiative could provide a base for such investment, and network these centres of competence, that each have monitored demonstration projects, to enhance expertise. Managed aquifer recharge stores water from wet periods where it has low or nuisance value, and recovers it for use in peak irrigation season or as a drought and emergency supply at high value. Investment in capacity development will be needed to capture these benefits. Finally, there is a great deal to be gained by sharing the success stories of effective groundwater governance and the results that have been achieved. These give confidence that groundwater is manageable using a variety of methods adapted to the local situation through participation by stakeholders. Some training may be needed for water resources managers in engaging with communities to help them recognize the problem they share in common and identify solutions that require collective effort to achieve their objectives. Particular help may be required where there are existing nonviable legal entitlements and where fossil groundwater is being used. 5