| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Historical alteration of freshwater systems worldwide | Compilation of data from the following sources: based on Naiman et al. 1995 as adapted from L’vovich and White 1990. Additional data from Shiklomanov 1997, ICOLD 1998, Avakyan and Iakovleva 1998, and IJHD 1998. |
| River channel fragmentation and flow regulation | Analysis was done by C. Nilsson, M. Svedmark, P. Hansson, S. Xiong, and K. Berggren, Landscape Ecology, Umeå University, Sweden. Additional data and analysis from Dynesius and Nilsson 1994. Rivers assessed are those with a historical record of more than 350 virgin mean annual discharge. Based on available information on dams and other flow regulations. Not all regions of the world were assessed. |
| Number of large dams under construction by river basin | IJHD 1998. This data set includes only reported dams over 60 meters high that are currently under construction, aggregated by river basin. |
| Residence time of continental runoff by river basin | Vörösmarty et al. 1997a. This indicator is based on the analysis of 622 of the largest reservoirs in the world (storage capacity at least 0.5 km3). The residence time of otherwise free flowing water is termed by the authors “aging of continental freshwater.” |
| Exploitation of groundwater resources | Compilation of data and case
studies are from the following sources:
EEA 1995, British Geological Survey 1996, Foster et al. 1998, and
Scheidleder et al. 1999. Wetlands extent and change in the United States and estimates for some European countries Data for the United States are from the National Wetlands Inventory, U.S. Fish and Wildlife Service (USFWS), and the Natural Resource Inventory of the U.S. Department of Agriculture. European data are from the European Environment Agency. |
| Percentage of cropland and urban and industrial land use by river basin | Cropland area is estimated from the Global Land Cover Characterization Database (GLCCD 1998) at lkm resolution. Cropland in this analysis excludes areas of mixed natural/cropland vegetation. Urban/industrial areas are based on NOAA-NGDC’s Stable Lights and Radiance Calibrated Lights of the World CD-ROM (1998). The data set contains the locations of stable lights, including frequently observed light sources, such as gas flares at oil drilling sites. Data were collected in 1994–95. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ? Although water in
rivers, lakes, and wetlands contains only 0.01
percent of the world’s freshwater and occupies less than 1 percent of
the Earth’s surface, the global value of freshwater services is
estimated in the trillions of U.S. dollars. ? Dams have a significant impact on freshwater ecosystems. Large dams have increased sevenfold in number since 1950 and now impound 14 percent of the world’s runoff. ? Sixty percent of the largest 227 rivers of the world are strongly or moderately fragmented by dams, diversions, and canals. In all, strongly or moderately fragmented systems account for nearly 90 percent of the total water volume flowing through these rivers. ? In the developing world, large dams are still being built at a fast rate, threatening the integrity of some of the remaining freeflowing rivers in the world. The basins with the greatest number of large dams currently under construction are the Yangtze, the Tigris and Euphrates, and the Danube. ? According to estimates by Vörösmarty et al. (1997a and 1997b), the average residence time of river water in regulated basins has tripled to over one month worldwide, whereas large reservoirs trap 30 percent of the global suspended sediments. ? Half the world’s wetlands are estimated to have been lost during the 20th century, as land was converted to agriculture and urban use, or filled to combat diseases, such as malaria. ? At least 1.5 billion people rely on groundwater as their only source of drinking water. Overexploitation and pollution in many regions of the world are threatening groundwater supplies, but comprehensive data on the quality and quantity of this resource are not available at the global level. |
? Global information on dams and
reservoirs is limited to dams that are
15 meters in height or greater, except for China, Japan, India, and
Spain, which report only on dams over 30 meters. The largest data gaps
are for Russia, which reports only on hydropower dams, and China, where
the majority of the world’s large dams have been built and for which
information is exceedingly difficult to acquire. ? The provision of latitude and longitude for each dam would highly improve our ability to locate these structures within the correct hydrological unit and assess their downstream impacts. ? Information on discharges is also lacking for many reservoirs; however, these data are needed to assess more fully the annual variations in river flow. ? Another important data set needed to assess freshwater ecosystem conditions is complete global information on wetlands distribution and change. Location and size of wetlands is especially needed for Asia, Africa, South America, the Pacific Islands, and Australia. ? Regional data for Oceania, Asia, Africa, eastern Europe, and the Neotropics allow for only cursory assessment of wetlands extent and location. Only North America and western Europe have better data and monitoring programs in place to track changes in wetlands area. ? Remote sensing data from the new Landsat 7 satellite and from radar, which can sense flooding underneath vegetation and can penetrate cloud cover, should improve the information base on the extent, location, and change in wetlands. ? Limited information is available on groundwater exploitation at the global level. National-level data exist but are not readily accessible or are not harmonized among countries. Groundwater information should be collected in coordination with data collection efforts on the effects of their use on other regional water resources, such as wetlands, lagoons, and river basins. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Annual renewable water supply per person by river basin in 1995 and projections for 2025 | CIESIN et al. (2000), Global Population Database.This database is based on census data for over 120,000 subnational administrative units for 1995. Water supply estimates are from a global runoff database developed by Fekete et al. (1999) at the University of New Hampshire in collaboration with the WMO/Global Runoff Data Centre in Germany. It combines observed discharge data with modeled runoff data. |
| Annual renewable water supply and dry season flow by river basin | Runoff estimates are from a global runoff database developed by Fekete et al. (1999). The dry season flow is estimated by selecting the four driest consecutive months of the year for each basin. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
? Between 1900 and 1995, water withdrawals increased sixfold, more than twice the rate of population growth. Dams and reservoirs have helped provide drinking water for much of the world’s population, increased agricultural output through irrigation, eased transport, and provided flood control and hydropower. ? Many regions of the world have ample water supplies, but currently more than 40 percent of the world’s population live in river basins experiencing water stress. ? As the world population grows from six to nine billion by the middle of the 21st century, we will become more dependent on irrigation for our food supplies, which will exacerbate the water scarcity problem in many regions and push other regions and populations to situations of water stress. ? By 2025, the PAGE analysis projects that, assuming current consumption patterns continue, at least 3.5 billion people or 48 percent of the world’s population will live in water-stressed basins. ? Based on the U.N. low-range population growth projection, 63 river basins are projected to have a population greater than 10 million by 2025. Of these river basins, 29 are already water stressed and will descend further into scarcity, 6 will move into water-stress conditions, and 12 additional basins may experience a strong negative change in water supply per person between 1995 and 2025. ? Low dry season flows have exacerbated water supply and quality problems in 27 basins with more than 10 million people in 1995. These basins include the Balsas and Grande de Santiago in Mexico, the Limpopo in Southern Africa, the Hai Ho and Hong in China, the Chao Phraya in Southeast Asia, and the Brahmani, Damodar, Godavari, Krishna, Mahi, Narmada, Ponnaiyar, Rabarmarti, and Tapti in India. |
? Statistics on water
availability and use at the global scale are
poor. In many parts of the world, we know less about water resources
than we did 20 years ago. The number of functioning hydrological
stations, for example, has fallen significantly since 1985. ? Current statistics of water withdrawals and consumption are fraught with uncertainty because of the highly decentralized nature of water use. ? Most estimates are based on a combination of modeled and observed data. ? In order to improve our ability to monitor the condition of freshwater systems to provide water for humans and ecosystems, better statistics on water availability and use are urgently needed, preferably at the watershed level so that impacts on entire ecosystems can be monitored. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Global concentrations of biochemical oxygen demand (BOD), phosphorous, and nitrates by river basin | Data are from UNEP’s Global Environmental Monitoring System (GEMS) Water Programme (1995). This project measured water quality in 82 major river basins from 1976 to 1990. Measurements are from a network of 175 sampling stations in around 60 countries. Because data from sampling points are extrapolated to the entire watershed, these data should be interpreted with caution |
| Trends in phosphorous and nutrient concentrations in Europe and the United States | Data for Europe are from the European Environment Agency. Data for the United States are from the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) program, and the USGS National Stream Quality Accounting Network (NASQAN). NASQAN monitors water quality in the four largest river systems in the United States: the Mississippi (including the Missouri and Ohio), the Columbia, the Colorado, and the Rio Grande. NAWQA performs detailed studies in 60 smaller basins across the United States, including Alaska and Hawaii. |
| Biological methods of water quality monitoring | Data are from studies from around the world, including the United States, France, India, the United Kingdom, and Australia. All studies illustrate applications of biological criteria to monitor water quality. Nitrate pollution in groundwater Data are from various sources and studies for China, India, western Europe, and the United States. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ? Water-borne
diseases from fecal contamination of surface waters
continue to be a major cause of mortality and morbidity in the
developing world. ? Surface water quality has improved in the United States and western Europe in the past 20 years with respect to some pollutants; however, nutrient loading from agricultural runoff continues to be a problem in these two regions. ? Worldwide water quality conditions appear to have degraded in almost all regions with intensive agriculture and large urban/industrial areas. ? Cases of algal blooms and eutrophication are being documented more frequently in most inland water systems around the world. ? Of the 82 major river basins in the world, those in North America, Europe, and Africa had the highest concentration of organic matter for the period 1976–90. ? Phosphorous concentration in U.S. waterways show improvement, whereas nitrate concentrations have remained more or less stable for the 1980-89 period. ? Evidence shows that nitrate pollution in groundwater, from fertilizer use, is getting worse in northern China, India, and Europe. Population increases in these areas and the need to increase agricultural production will require increase use of fertilizers, which will exacerbate the groundwater pollution problem. |
? Data on water quality at the
global level is very scarce. There have
been very few sustained programs to monitor water quality worldwide. ? Information is usually limited to industrial countries or small, localized areas. ? Water monitoring is also almost exclusively limited to chemical pollution rather than biological monitoring, which would provide a better understanding of the condition of the system. For regions, such as Europe, where some monitoring is taking place, difference in measures and approaches make the data hard to compare. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Historical change in fish catch and species composition for selected rivers, lakes, and inland seas. | Data are from various sources for the following bodies of water: Danube, Rhine, Missouri, Great Lakes, Illinois, Pearl (Xi Jiang), Lake Victoria, Colorado in the United States, and the Aral Sea. All studies looked at either changes in species composition or changes in commercial landings of important inland fisheries. |
| Recent trends in catch statistics from inland waters | Inland capture fisheries data are from the Food and Agriculture Organization of the United Nations (FAO) for the period 1984–97. Inland capture fisheries include freshwater and diadromous fish caught in inland waters, and freshwater molluscs and crustaceans. |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ? In 1997, inland
fisheries landings accounted for 7.7 million metric
tons, or almost 12 percent of total capture available for human
consumption, a level estimated to be at or above maximum sustainable
yields. Taking into account the inland capture, fisheries are estimated
to be underreported by two or three times, the contribution to direct
human consumption is likely to be at least twice as high. ? Freshwater aquaculture currently has a higher production than capture fisheries, contributing 17.7 million metric tons of fish and seafood in 1997. In 1997, marine and inland aquaculture production provided 30 percent of the fish for human consumption; 60 percent of this production comprised of freshwater finfish or fish that migrate between fresh and saltwater. ? At the global level, inland fisheries landings have been increasing since 1984. Most of this increase has occurred in Asia, Africa, and more moderately in Latin America. In North America, Europe, and the former Soviet Union, landings have declined, whereas in Oceania they have remained stable. ? Despite this increase in landings, maintained in many regions by fishery enhancements, such as stocking and fish introductions, the greatest overall threat for the long-term sustainability of inland fishery resources is the loss of fishery habitat and the degradation of the terrestrial and aquatic environment. ? Historical trends in commercial fisheries data for well-studied rivers show dramatic declines over the 20th century, mainly from habitat degradation, invasive species, and overharvesting. |
? Data on inland fisheries
landings are poor, especially in developing
countries. The FAO database on inland fisheries landings is the most
complete data set at the global level; however, it has important
limitations. Some of the main problems are that much of the catch is
not reported at the species level and much of the fish consumed locally
is never reported, making fishery assessment difficult. ? There is no systematic data collection on the contribution of stocking, fish introductions, and other enhancement programs to inland fisheries. This information, as well as information on recreational fisheries, which are becoming increasingly important in many countries, should be incorporated into data collection efforts. ? Reporting on fishery resources at the watershed level instead of the national level, as it has been done to date, would improve our understanding of the condition of the system and the linkages between upstream activities and their downstream effects. This information could then be applied to watershed and fishery resources management plans. ? Historical trends in fisheries statistics are available only for a few well-studied rivers, and because of the multispecies composition of the catch in most inland water bodies, particularly in developing countries, assessments on the condition of the resources are hard to carry out. |
| PAGE MEASURES AND INDICATORS | DATA SOURCES AND COMMENTS |
| Important areas and ecoregions for freshwater biodiversity | Olson and Dinerstein 1999 and Groombridge and Jenkins 1998. Both analyses are priority-setting exercises for conservation, based on existing data and expert opinion. |
| Fish species richness and endemism by river basin | Revenga et al. 1998. Data compiled for the World Resources Institute by the World Conservation Monitoring Centre (WCMC). Additional information comes from Kottelat and Whitten (1996) and Oberdorff (1997). |
| Biological distinctiveness index for North America | Abell et al. 2000. Regional priority-setting analysis for conservation, based on a combination of existing environmental data and expert opinion. |
| Bird population trends in the United States and Canada | Data are from the North American Breeding Bird Survey, which is organized by the Patuxent Environmental Science Center. Data used in this report are limited to wetland-dependent species. Population trends cover the period 1966–98. Global amphibian population census Data are from the Declining Amphibian Populations Task Force (DAPTF). DAPTF is a network of more than 3,000 scientists working in 90 countries. |
| Threatened species and habitats in North America, the Middle East, and Europe | Data for North America are from Abell et al. 2000. These data cover threat status for North American fish and reptile species. Data for Europe and the Middle East are from BirdLife International. Data are for threatened bird species and important bird areas in these two regions |
| Presence of nonnative species: introduced fish, zebra mussel in the United States, and water hyacinth distribution | Introduced fish species information is from FAO’s Database on Introductions of Aquatic Species (DIAS). Data on zebra mussel expansion are from the USGS Nonindigenous Aquatic Species (NAS) information resource. Data on global distribution of water hyacinth are from a variety of sources. Water hyacinth distrubution in the United States is from the Aquatic Nuisance Species Task Force, cochaired by the USFWS and the National Oceanic and Atmospheric Administration (NOAA). |
| CONDITIONS AND TRENDS | INFORMATION STATUS AND NEEDS |
| ? Freshwater
ecosystems harbor an extraordinary concentration of
species; approximately 300 new freshwater species are described each
year. World Wildlife Fund-US (WWF-US) has identified 53 freshwater
ecoregions around the world as priority areas for conservation, based
on their unique assemblage of species, habitats, and ecological or
evolutionary phenomena, while the WCMC has identified 136 areas of high
freshwater biodiversity around the world. ? Physical alteration, habitat loss and degradation, water withdrawal, pollution, overexploitation, and the introduction of nonnative species all contribute to declines in freshwater species. ? More than 20 percent of the world’s freshwater fish have become extinct or been threatened or endangered in recent decades. ? Of the 108 large basins analyzed, 27 have high fish species richness. More than half of these basins are in the tropics, and the rest are in central North America, India, and China. ? Evidence shows that freshwater species, such as amphibians, fish, and wetland-dependent birds, are at high risk of imperilment in many regions of the world. In the United States and parts of Canada, however, 66 percent of the populations of wetland birds are increasing. ? The intentional or accidental introduction of nonnative species in freshwater systems is a global phenomenon. Evidence for North America, one of the best-documented regions, shows that the introduction of alien species not only has contributed to the extinction and imperilment of native fauna but also has substantial associated economic costs. ? Modeled estimates of future species extinction rates suggest that the rates for freshwater animal species are five times higher than for terrestrial species. ? The growing concern for species, the maintenance of pristine habitats, and the need to maintain other goods and services, such as clean water, is driving the trend, in some countries, to restore and rehabilitate freshwater systems. |
? Direct measurements of the condition of biodiversity in freshwater systems are sparse worldwide. Basic information on freshwater species for many developed nations and most of the developing world is lacking, as well as threat-analyses for most freshwater species. This makes analyzing population trends impossible or limited to a handful of wellknown species. ? Information on nonnative species is frequently anecdotal and often limited to records of the presence of a particular species, without documentation of the effects on the native fauna and flora. Spatial data on invasive species are available for few species, mostly in the United States and Australia. ? Excellent trend data are available for bird populations in the United States and Canada, and other available regional data are good but lack long-term population trends, such as data on the distribution of important bird areas from BirdLife International. ? At a minimum, there should be monitoring of key indicator species and monitoring of the presence or introduction of nonnative species and their impacts on native fauna and flora. |