EarthTrends: Featured Topic Title: Giving Nature Its Share: Reserving Water for Ecosystems Authors: Vladimir Smakhtin, Carmen Revenga, Petra Doll, Rebecca Tharme Source: Putting the w ater Requirements of Freshwater Ecosystems into the Global picture of w ater Resources Assesment Date Written: April 2003 Modern assessments of water cological processes. A water then ascertaining the minimum focus largely on the availability of regime is the prevailing pattern of quantity of water needed to water for unrestricted human use, water flow for that system, over a sustain them but have yet to explicitly consider given time. Some rivers have a Unfortunately, population the environmental needs of the naturally constant flow of water growth, industrialization, and higher seasonal flood of irrigat provide for the sustainable Intermittent rivers in arid uriculture have increased utilization of water resources areas. on the other hand. do not demand for many water-related such assessments must determine have a constant flow but rather goods and services, straining the the extent to which a river's flow periods of high peak flows. Native apacity of freshwater can be altered from its natural species are accustomed to and rely ecosystems. These phenomena ondition, while still maintaining on these flow patterns for their make water scarcity a top the integrity or an acceptable level survival. Determining priority for many countries of degradation of the environmental water requirements Ideally, only the excess water in Worldwid or an ecosystem involves the system-the amount of water need has produced the concept of identifying those aspects of the above and bevond what the “ environmental flows”or natural water regime that are most ecosystem requires to maintain “ environmental water important for sustaining its key equirements ecosystem features and processes dependent species-should be Environmental taken for agricultural, water requirements are Visualizing Water Scarcity domestic, or industrial defined as the quali uses. However, in reality and quantity of water SAFE case required by an aquatic Actual Use Observing environmental ecosystem for the protection and Utz able demands will guide wise Total Water Water resource use by providing Available for water withdrawals and dependent species Environmental Need The Global Picture sustain the crucial water-related goods WATER STRESSED The study of depend upon to requirements of aquatic survive, a certain Utilizable amount of w: Total Water Actual use ecosystems is a rapidly be reserved for them Available methods for estimating environmental water The Needs of Environmental Needs requirements differ in Ecosystems requirements, types of WATER SCARCE d Freshwater ecosystems A ctual us time required for fapping into Utilizable application, and the level tal areas neo Total Water environmental Water f confidence in the final maintained water Available wafer needs estimates. They range from hydrological their plant and animal Emvironmental methods, largely data- communities and driven, to multidisciplinary
EarthTrends: Featured Topic Title: Giving Nature Its Share: Reserving Water for Ecosystems Authors: Vladimir Smakhtin, Carmen Revenga, Petra Döll, Rebecca Tharme Source: Putting the Water Requirements of Freshwater Ecosystems into the Global Picture of Water Resources Assessment Date Written: April 2003 Modern assessments of water focus largely on the availability of water for unrestricted human use, but have yet to explicitly consider the environmental needs of the aquatic ecosystems. In order to provide for the sustainable utilization of water resources, such assessments must determine the extent to which a river’s flow can be altered from its natural condition, while still maintaining the integrity or an acceptable level of degradation of the eco system. Worldwide recognition of this need has produced the concept of “environmental flows” or “environmental water requirements.” Environmental water requirements are defined as the quality and quantity of water required by an aquatic ecosystem for the protection and maintenance of its structure, functioning, and dependent species. If ecosystems are to sustain the crucial water-related goods and services humans depend upon to survive, a certain amount of water must be reserved for them. The Needs of Aquatic Ecosystems Freshwater ecosystems and their associated coastal areas need maintained water regimes to support their plant and animal communities and ecological processes. A water regime is the prevailing pattern of water flow for that system, over a given time. Some rivers have a naturally constant flow of water with higher seasonal floods. Intermittent rivers in arid areas, on the other hand, do not have a constant flow, but rather periods of high peak flows. Native species are accustomed to and rely on these flow patterns for their survival. Determining environmental water requirements for an ecosystem involves identifying those aspects of the natural water regime that are most important for sustaining its key ecosystem features and processes, then ascertaining the minimum quantity of water needed to sustain them. Unfortunately, population growth, industrialization, and the expansion of irrigated agriculture have increased demand for many water-related goods and services, straining the capacity of freshwater ecosystems. These phenomena make water scarcity a top priority for many countries. Ideally, only the excess water in the system–the amount of water above and beyond what the ecosystem requires to maintain its ecological processes and dependent species–should be taken for agricultural, domestic, or industrial uses. However, in reality, this is rarely the case. Observing environmental demands will guide wise resource use by providing specific target benchmarks for water withdrawals. The Global Picture The study of environmental water requirements of aquatic ecosystems is a rapidly developing field. Current methods for estimating environmental water requirements differ in input information requirements, types of designated ecosystems, time required for application, and the level of confidence in the final estimates. They range from hydrological methods, largely datadriven, to multidisciplinary models, involving expert
2 panel discussions and ecological Preliminary results of the in which water scarcity is information study portray a bleak picture of the As a rule, ecosystem water condition of the world's river withdrawal to water availability equirements are casespecific basins. In many parts of the world, without taking into account the nd must be carried out at the humans are tapping into water that environs nental needs of aquatic cale of individual nver basins. is needed to sustain healthy systems. This is the approach Water Scarcity: The Traditional view used in most current water resources Figure 2: Human Water Stress by River Basin Water Use as a Proportion of Total Water Availability assessment models and scenarios. The following map(Fig 3)measures the withdrawal with ailable to human Uater Stress Indica减 use. where the portion of the basins 03-04 water that is stimated to constitute an environmental water requirement is not opcn Major River Basins A comparison of the Taking Environmental Water Requirements Into Account wo maps shows that hen the ecosystems Figure 3: Human Infringement on Environmental Water Demand ater withdrawal as a proportion of w ater Available for Human Use water requiremen are taking into account. more basins ave a high degree of water stress. In addition. the circles in Fig 3 identify ang Ho (Yellow) Basin Chin basins where Uater Stress Indicator excessive extraction of water is causing problems to the ecosystem and to the Orange River Basin at depend on the environmental No Discharge Australia ervices that the Major River Basins ecosystem provides In an effort to gauge the general ecosystems, damaging the The future off of the world's water livelihoods of fishers and local Environmental Water resources situation. however a communities.Incorporating global model of water availability environmental requirements into Requirements at takes ecosystem water assessments highlights long requirements into account was ignored, yet vital, aspects of water A few countries, including developed by the International scarcity. This new information Australia, the United States, and Water Management Institute, the shows the worlds water resources World Resources Institute to be in a much more troubling track record of applying Center for environmental state than originally assume different water assessment Systems Research, and the World The top map (Fig. 2 methodologies. Sadly, they Conservation Union in 200 represents the traditional method make up the exception rather OEarthTrends 2003 World Resources Institute. All nights reserved. Fair use is permitted on a limited scale and for educational purposes
©EarthTrends 2003 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 2 panel discussions and ecological information. As a rule, ecosystem water requirements are case-specific, and must be carried out at the scale of individual river basins. In an effort to gauge the general state of the world’s water resources situation, however, a global model of water availability that takes ecosystem requirements into account was developed by the International Water Management Institute, the World Resources Institute, the Center for Environmental Systems Research, and the World Conservation Union in 2003. Preliminary results of the study portray a bleak picture of the condition of the world’s river basins. In many parts of the world, humans are tapping into water that is needed to sustain healthy ecosystems, damaging the livelihoods of fishers and local communities. Incorporating environmental requirements into water assessments highlights longignored, yet vital, aspects of water scarcity. This new information shows the world’s water resources to be in a much more troubling state than originally assumed. The top map (Fig. 2) represents the traditional method in which water scarcity is assessed. It compares water withdrawal to water availability without taking into account the environmental needs of aquatic systems. This is the approach used in most current water resources assessment models and scenarios. The following map (Fig. 3) measures the proportion of water withdrawal with respect to water available to human use, where the portion of the basin’s water that is estimated to constitute an environmental water requirement is not open for human use. A comparison of the two maps shows that when the ecosystem’s water requirements are taking into account, more basins have a high degree of water stress. In addition, the circles in Fig. 3 identify perfect examples of basins where excessive extraction of water is causing problems to the ecosystem and to the people that depend on the environmental services that the ecosystem provides. The Future of Environmental Water Requirements A few countries, including Australia, the United States, and South Africa, possess a solid track record of applying different water assessment methodologies. Sadly, they make up the exception rather
than the rule. Most nations. even ortunately, a few ongoing those privileged with considerable freshwater assessments and financial and technical resources, initiatives currently focus on lack the information necessary to improving access to basin-level determine or even estimate data as well as information on environmental freshwater ecosystem goods requirements. The ervices and resources. Firmly aforementioned global model establishing accurate environmental elies exclusively on hydrological water requirements would data and simple conceptual rules, necessitate the collection and but ideally, basin-level nalysis of local and /or region nvironmental requirement information in the context of should also factor in water variable flows. This would allow quality, biodiversity, runoff, for a better understanding and drought conditions, the desired quantification of hydrology future state of a basin. and realistic management targets for differences in availability of water different ecosystems, basins, and during different seasons of the regions; and the proper evaluation ear. The scarcity of such data f trade-offs. It is envisaged that kes the obstacle of measuring information generated through nvironmental water uch initiatives will reinforce th equirements an even greater case for environmental water challenge requirements and provide insights into their development. OEarthTrends 2003 World Resources Institute. All nights reserved. Fair use is permitted on a limited scale and for educational purposes
©EarthTrends 2003 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 3 than the rule. Most nations, even those privileged with considerable financial and technical resources, lack the information necessary to determine or even estimate environmental water requirements. The aforementioned global model relies exclusively on hydrological data and simple conceptual rules, but ideally, basin-level environmental requirements should also factor in water quality, biodiversity, runoff, drought conditions, the desired future state of a basin, and differences in availability of water during different seasons of the year. The scarcity of such data makes the obstacle of measuring environmental water requirements an even greater challenge. Fortunately, a few ongoing freshwater assessments and initiatives currently focus on improving access to basin-level data, as well as information on freshwater ecosystem goods, services and resources. Firmly establishing accurate environmental water requirements would necessitate the collection and analysis of local and/or regional information in the context of variable flows. This would allow for a better understanding and quantification of hydrology; realistic management targets for different ecosystems, basins, and regions; and the proper evaluation of trade-offs. It is envisaged that information generated through such initiatives will reinforce the case for environmental water requirements and provide insights into their development
REFERENCES Abell,RA, D.M. Olson, E. Dinerstein, P.T. Hurley, J.T. Diggs, W. Eichbaum, S. Walters, W. Wettengel, T Allnutt, C J. Loucks, and P. Hedao. 2000. Freshwater Ecoregions of North America: A Conservation Assessment, Washington, DC: World Wildlife Fund-United States Alcamo, J, Doll, P, Henrichs, T, Kaspar, F, Lchner, B, ROsch, T, Siebert, S: WaterGAP 2(2002): A model for global assessment of freshwater resources. Hydrological Sciences Journal. (in pres Bovee, K.D. (1982)A guide to stream habitat analysis using the Instream Flow Incremental methodology. US Fish and Wildlife Service. Biological Services Program, Cooperative Instream Flow Service Group. Instream Flow Information Paper No 12, FWS/OBS-82/26, Fort Collins, CO, USA, 248 pp Doll, P, Kaspar, F and Lehner, B(2000)World water in 2025: global modeling and scenario analysis. In Rijsberman, F.R.(Ed World Water Scenarios: Analyses. Earthscan Publications. 396 Pp Doll, P, Kaspar, F, Lehner, B (2002): A global hydrological model for deriving water availability indicators: model tuning and validation. J Hydrol. (in press) DolL, P, Smakhtin, V, Revenga, C, Tharme, R Putting the Water Requirements of Freshwater Ecosystems into the Global Picture of Water Resources Assessment. Draft paper presented at the 3rd World Water Forum, Kyoto, Japan, March 18th, 2003 Durban, M.J., Gustard, A. Acreman, M. C", Elliott, C.R. N.(1998)Review of overseas approaches to setting river flow objectives. Environmental Agency R&D Technical Report W6B(964. Institute of Hydrology, Wallingford UK, 61 Pp ekete, B M, Vorosmarty, C.J., Grabs, W.(1999) Global composite runoff fields of observed river discharge and simulated water balances. Report No 22, Global Runoff Data Centre, Koblenz, Germany Conservation Monitoring Centre, Cambridge, U.K.: World Conservation Press. Obal Assessment.World Groombridge B and M. Jenkins. 1998. Freshwater Biodiversity: a Preliminary glol Haines, A.T., Finlayson, B L. and McMahon, T A (1988)A global classification of river regimes. Applied Geography 8: 255-272 Hughes, D.A. and Munster, F(2000) Hydrological information and techniques to support the determination of water quantity component of the ecological reserve for rivers. Water Research Commission Report No TT 137/00, Pretoria, South Africa. 91 pp Karim K, Gubbels, M.E. and Goulter, IC(1995) Review of determination of instream flow requirements with special application to Australia. Water Res. Bull. 31(6): 1063-1077 King, J and Louw, D(1998)Instream flow assessments for regulated rivers in South Africa using Building Block Methodology. Aquatic Ecosystems Health and management, 1: 109-124 Korzun, V.I. Sokolov, A.A., Budyko, M.I., Voskresensky, K P, Kalinin, G.P., Konoplyansev, A.A., Korotkevich, ES, Kuzin, P.S. Lvovich, M.I.(eds ) .(1978)World Water Balance and Water Resources of the Earth UNESCO. Paris Oki, T, Agata, Y, Kanae, S, Saruhashi, T, Yang, D and Musuake, K. 2001) Global assessment of current water resources using total runoff integrating pathways. Hydrol. Sci. J. 46(6): 983-995 Poff, N.L., Allan, J D, Bain, M.B., Karr, J.R., Prestegaard, K.L. Richter, B D Sparks, R.E. and Stromberg, J C (1997) The natural flow regime: a paradigm for river conservation and restoration. Bioscience 47( 11): 769-784 OEarthTrends 2003 World Resources Institute. All nights reserved. Fair use is permitted on a limited scale and for educational purposes
©EarthTrends 2003 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 4 REFERENCES Abell, R.A., D.M. Olson, E. Dinerstein, P.T. Hurley, J.T. Diggs, W. Eichbaum, S. Walters, W. Wettengel, T. Allnutt, C.J. Loucks, and P. Hedao. 2000. Freshwater Ecoregions of North America: A Conservation Assessment, Washington, DC: World Wildlife Fund-United States. Alcamo, J., Döll, P., Henrichs, T., Kaspar, F., Lehner, B., Rösch, T., Siebert, S.: WaterGAP 2 (2002): A model for global assessment of freshwater resources. Hydrological Sciences Journal. (in press) Bovee, K.D. (1982) A guide to stream habitat analysis using the Instream Flow Incremental methodology. US Fish and Wildlife Service. Biological Services Program, Cooperative Instream Flow Service Group. Instream Flow Information Paper No 12, FWS/OBS-82/26, Fort Collins, CO, USA, 248 pp Döll,P., Kaspar, F. and Lehner, B. (2000) World water in 2025: global modeling and scenario analysis. In: Rijsberman, F.R. (Ed.) World Water Scenarios: Analyses. Earthscan Publications. 396 pp Döll, P., Kaspar, F., Lehner, B. (2002): A global hydrological model for deriving water availability indicators: model tuning and validation. J. Hydrol. (in press) Döll, P., Smakhtin, V., Revenga, C., Tharme, R. Putting the Water Requirements of Freshwater Ecosystems into the Global Picture of Water Resources Assessment. Draft paper presented at the 3rd World Water Forum, Kyoto, Japan, March 18th, 2003. Durban, M.J., Gustard, A. Acreman, M.C., Elliott, C.R.N. (1998) Review of overseas approaches to setting river flow objectives. Environmental Agency R&D Technical Report W6B (96)4. Institute of Hydrology, Wallingford, UK, 61 pp Fekete, B.M., Vörösmarty, C.J., Grabs, W. (1999) Global composite runoff fields of observed river discharge and simulated water balances. Report No 22, Global Runoff Data Centre, Koblenz, Germany Groombridge B. and M. Jenkins. 1998. Freshwater Biodiversity: a Preliminary Global Assessment. World Conservation Monitoring Centre, Cambridge, U.K.: World Conservation Press. Haines, A.T., Finlayson, B.L. and McMahon, T.A. (1988) A global classification of river regimes. Applied Geography 8: 255-272 Hughes, D.A. and Münster, F. (2000) Hydrological information and techniques to support the determination of water quantity component of the ecological reserve for rivers. Water Research Commission Report No TT 137/00, Pretoria, South Africa. 91 pp Karim K., Gubbels, M.E. and Goulter, I.C. (1995) Review of determination of instream flow requirements with special application to Australia. Water Res. Bull. 31(6): 1063 -1077 King, J. and Louw, D (1998) Instream flow assessments for regulated rivers in South Africa using Building Block Methodology. Aquatic Ecosystems Health and Management, 1: 109-124 Korzun, V.I. Sokolov, A.A., Budyko, M.I., Voskresensky, K.P., Kalinin, G.P., Konoplyansev, A.A., Korotkevich, E.S., Kuzin, P.S. L'vovich, M.I. (eds.). (1978) World Water Balance and Water Resources of the Earth. UNESCO, Paris Oki, T., Agata, Y, Kanae, S., Saruhashi, T, Yang, D and Musuake, K. (2001) Global assessment of current water resources using total runoff integrating pathways. Hydrol. Sci. J. 46(6): 983-995 Poff, N.L., Allan, J.D.,Bain, M.B., Karr, J.R., Prestegaard, K.L. Richter, B.D. Sparks, R.E. and Stromberg, J.C. (1997) The natural flow regime: a paradigm for river conservation and restoration. Bioscience 47 (11): 769-784
Raskin, P, Gleick, P, Kirshen, P, Pontius, G, Strzepek, K,(1997)Water futures: Assessment of long-ramge patterns and problems. Background paper for Comprehensive Assessment of the Freshwater Resources of the World, Stockholm Environment Institute, Stockholm, Sweeden Revenga, C, Brunner, J, Henninger, N. Kassem, K and Payne, R.( 2000). Pilot Analysis of Freshwater Ecosystems: Freshwater Systems. World Resources Institute, Washington, DC, USA, 83 Revenga, C. Murray, S, Abramovitz, J. and Hammond, A(1998)Watersheds of the World ecological value and ulnerability. A joint publication by the World Resources Institute and WorldWatch In gton, DC Richter, B.D., Baumgartner, J.V., Wigington, R, Braun, D P (1997) How much water does a river need Freshwater Biology 37: 231-249 Rosenberg, D.M., McCully, P and Pringle, C.M. (2000) Global-scale Environmental Effects of Hydrological Alterations: Introduction. BioScience 50(9): 746-751 Smakhtin, VU(2001) Low flow hydrology: a review. J HydroL. 240: 147-186 Tennant, D L(1976) Instream flow regimens for fish, wildlife, recreation and related environmental resources. Fisheries 1(4): 6-10 Tharme, R.E. (1996)Review of international methodologies for the quantification of the instream flow requirements of rivers. Water law review. Final Report for policy development. Commissioned by the Department of Water Affairs and Forestry, Pretoria, Freshwater Research Unit. University of Cape Town, Cape Town, South Africa, 116 Pp Vogel,R.M.& Fennessey, NM.(1995)Flow duration curves II: A review of applications in water resources planning. Water Res Bull, 31(6): 1029-1039 Vorosmarty, C.J., P. Green, P, Salisbury, J, Lammers, R.B.(2000): Global water resources: vulnerability from nate change and population growth. Science 289, 284-288. OEarthTrends 2003 World Resources Institute. All nights reserved. Fair use is permitted on a limited scale and for educational purposes
©EarthTrends 2003 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 5 Raskin, P., Gleick, P., Kirshen, P., Pontius, G, Strzepek, K., (1997) Water futures: Assessment of long-ramge patterns and problems. Background paper for Comprehensive Assessment of the Freshwater Resources of the World, Stockholm Environment Institute, Stockholm, Sweeden Revenga, C.,Brunner, J., Henninger, N. Kassem, K.and Payne, R. (2000). Pilot Analysis of Freshwater Ecosystems: Freshwater Systems. World Resources Institute, Washington, DC., USA, 83 pp. Revenga, C. Murray, S., Abramovitz, J. and Hammond, A. (1998) Watersheds of the World : ecological value and vulnerability. A joint publication by the World Resources Institute and WorldWatch Institute, Washington, DC., USA, 197 pp. Richter, B.D., Baumgartner, J.V., Wigington, R., Braun, D.P. (1997) How much water does a river need ? Freshwater Biology 37: 231-249 Rosenberg, D.M., McCully, P. and Pringle, C.M. (2000) Global-scale Environmental Effects of Hydrological Alterations: Introduction. BioScience 50(9): 746-751 Smakhtin, V.U. (2001) Low flow hydrology: a review. J. Hydrol. 240: 147-186 Tennant, D.L. (1976) Instream flow regimens for fish, wildlife, recreation and related environmental resources. Fisheries 1(4): 6-10 Tharme, R.E. (1996) Review of international methodologies for the quantification of the instream flow requirements of rivers. Water law review. Final Report for policy development. Commissioned by the Department of Water Affairs and Forestry, Pretoria, Freshwater Research Unit. University of Cape Town, Cape Town , South Africa, 116 pp Vogel, R.M. & Fennessey, N.M. (1995) Flow duration curves II: A review of applications in water resources planning. Water Res. Bull., 31(6): 1029 - 1039 Vörösmarty, C.J., P.Green, P., Salisbury, J., Lammers, R.B. (2000): Global water resources: vulnerability from climate change and population growth. Science 289, 284-288