Managing River Flows for Ecological Integrity

Ecological Applications, 13(1), 2003, pp. 206±224 ᭧ 2003 by the Ecological Society of America

ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT: MANAGING RIVER FLOWS FOR ECOLOGICAL INTEGRITY

BRIAN D. RICHTER,1,5 RUTH MATHEWS,2 DAVID L. HARRISON,3 AND ROBERT WIGINGTON4 1The Nature Conservancy, 490 West®eld Road, Charlottesville, Virginia 22901 USA 2The Nature Conservancy, 410 North 4th Street, Mt. Vernon, Washington 98273 USA 3Moses, Wittemyer, Harrison, and Woodruff, P.O. Box 1440, Boulder, Colorado 80306-1440 USA 4The Nature Conservancy, 2060 Broadway, Suite 230, Boulder, Colorado 80302 USA

Abstract. Human demands on the world's available freshwater supplies continue to grow as the global population increases. In the endeavor to manage water to meet human needs, the needs of freshwater species and ecosystems have largely been neglected, and the ecological consequences have been tragic. Healthy freshwater ecosystems provide a wealth of goods and services for society, but our appropriation of freshwater ¯ows must be better managed if we hope to sustain these bene®ts and freshwater biodiversity. We offer a framework for developing an ecologically sustainable water management program, in which human needs for water are met by storing and diverting water in a manner that can sustain or restore the ecological integrity of affected river ecosystems. Our six-step process includes: (1) developing initial numerical estimates of key aspects of river ¯ow necessary to sustain native species and natural ecosystem functions; (2) accounting for human uses of water, both current and future, through development of a computerized hydrologic simulation model that facilitates examination of human-induced alterations to river ¯ow regimes; (3) assessing incompatibilities between human and ecosystem needs with particular attention to their spatial and temporal character; (4) collaboratively searching for solutions to resolve incompatibilities; (5) conducting water management experiments to resolve critical uncertainties that frustrate efforts to integrate human and ecosystem needs; and (6) designing and implementing an adaptive management program to facilitate ecologically sustainable water management for the long term. Drawing from case studies around the world to illustrate our framework, we suggest that ecologically sustainable water management is attainable in the vast majority of the world's river basins. However, this quest will become far less feasible if we wait until water supplies are further over-appro- priated. Key words: adaptive management; biodiversity; dam operations; ecological ¯ow assessment; ecosystem management; ecosystem monitoring; freshwater ecosystems; hydrologic alteration; instream ¯ow; river management; sustainable water development; water resources management.

It is one thing to ®nd fault with an existing system. ically centers on managing human uses of water such It is another thing altogether, a more dif®cult task, that enough water of suf®cient quality is available for to replace it with another approach that is better. use by future generations. In the endeavor to manage water to meet various ÐNelson Mandela, 16 November 2000 human needs, however, the water needs of freshwater (speaking of water resource management) species and ecosystems have been largely neglected. In many areas of the world, growing human popu- The ecological consequences have been tragic (IUCN lations are rapidly depleting available freshwater sup- 2000, Pringle et al. 2000, Stein et al. 2000, Baron et plies. During the 20th century, the global human pop- al. 2002). The alteration of river ¯ow regimes asso- ulation increased fourfold to more than six billion (6 ciated with dam operations has been identi®ed as one ϫ 109). Water withdrawn from natural freshwater eco- of three leading causes, along with nonpoint source systems increased eightfold during the same period pollution and invasive species, of the imperilment of (Gleick 1998). Facing an ominous specter of increas- aquatic animals (Richter et al. 1997a, Pringle et al. ingly severe water-supply shortages in many areas of 2000). Freshwater ecosystem services and products the world, social planners and government leaders are valued by society have been severely compromised as exploring strategies for managing water resources sus- well (Postel and Carpenter 1997, IUCN 2000). tainably (IUCN 2000). This quest for sustainability typ- The water needs of humans and natural ecosystems are commonly viewed as competing with each other. Manuscript received 26 September 2001; revised 12 April Certainly, there are limits to the amount of water that 2002; accepted 22 April 2002; ®nal version received 31 May 2002. Corresponding Editor: J. S. Baron. can be withdrawn from freshwater systems before their 5 E-mail: [email protected] natural functioning and productivity, native species, 206 February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 207 and the services and products they provide become 1996). Traditional water management has generally severely degraded. Water managers and political lead- sought to dampen the natural variability of river ¯ows ers are becoming increasingly cognizant of these limits to attain steady and dependable water supplies for do- as they are being confronted with endangered species mestic and industrial uses, irrigation, navigation, and or water quality regulations, and changing societal val- hydropower, and to moderate extreme water conditions ues concerning ecological protection. During the past such as ¯oods and droughts. For instance, by storing decade, many examples have emerged from around the water in reservoirs, water managers capture high ¯ows world demonstrating ways of meeting human needs for during wet years or seasons to supplement water sup- water while sustaining the necessary volume and tim- plies at drier times, thereby maximizing the reliability ing of water ¯ows to support affected freshwater eco- of water supplies and certain economic bene®ts each systems. In fact, we believe that the compatible inte- year. gration of human and natural ecosystem needs (iden- When natural variability in river ¯ows is altered too ti®ed here as ecologically sustainable water manage- much, marked changes in the physical, chemical, and ment) should be presumed attainable until conclusively biological conditions and functions of natural fresh- proven otherwise. We offer this touchstone for such water ecosystems can be expected. When changes to efforts: natural ¯ow regimes are excessive, causing a river ecosystem to degrade toward an altered character, the costs Ecologically sustainable water management protects are high to both biodiversity and society (Postel and the ecological integrity of affected ecosystems while Carpenter 1997, IUCN 2000, WCD 2000) (Fig. 1). The meeting intergenerational human needs for water transition to a new, altered ecosystem state can take and sustaining the full array of other products and tens to hundreds of years as chain reactions cascade services provided by natural freshwater ecosystems. through second- and third-order effects within an eco- Ecological integrity is protected when the compo- system (Petts and Calow 1996, IUCN 2000), thereby sitional and structural diversity and natural func- obscuring original causes. tioning of affected ecosystems is maintained. Water management for human use necessarily alters In this paper we offer a general framework for de- a river's natural ¯ow regime in various ways. However, veloping an ecologically sustainable water manage- there is some degree and types of alteration that will ment program, drawing upon examples from around not jeopardize the viability of native species and the the United States and beyond to illustrate its essential ability of an ecosystem to provide valuable products elements, with a focus on river systems. Before we and services for society. Around the world, river sci- elaborate on the elements of this framework, we further entists are seeking better understanding of the ways discuss the ecological degradation that we seek to al- and degrees to which river ¯ows can be modi®ed for leviate. human purposes while maintaining an adequate sem- blance of the composition, structure, and function of NATURAL VS.MANAGED FLOW VARIABILITY natural ecosystems (Poff et al. 1997, Richter et al. Ecological degradation has generally been an unin- 1997b, Arthington and Zalucki 1998, King and Louw tended consequence of water management, stemming 1998, Tharme, in press). from a lack of understanding of water ¯ows necessary TOWARD ECOLOGICAL SUSTAINABILITY to sustain freshwater ecosystems. Natural freshwater ecosystems are strongly in¯uenced by speci®c facets The ultimate challenge of ecologically sustainable of natural hydrologic variability. Of particular impor- water management is to design and implement a water tance are seasonal high and low ¯ows, and occasional management program that stores and diverts water for ¯oods and droughts (Stanford et al. 1996, Poff et al. human purposes in a manner that does not cause af- 1997, Richter et al. 1997b). A river's ¯ow regime is fected ecosystems to degrade or simplify. This quest now recognized as a ``master variable'' that drives var- for balance necessarily implies that there is a limit to iation in many other components of a river ecosystem, the amount of water that can be withdrawn from a river, e.g., ®sh populations, ¯oodplain forest composition, and a limit in the degree to which the shape of a river's nutrient cycling, in both direct and indirect ways natural ¯ow patterns can be altered. These limits are (Sparks 1995, Walker et al. 1995, Poff et al. 1997; de®ned by the ecosystem's requirements for water. Hu- Instream Flow Council [available online]6). The ex- man extraction or manipulation that exceeds these lim- traordinary species richness and productivity charac- its will, in time, compromise the ecological integrity teristic of freshwater ecosystems is strongly dependent of the affected ecosystems, resulting in the loss of na- upon, and attributable to, the natural variability of their tive species and valuable ecosystem products and ser- hydrologic conditions. vices for society. But variability runs counter to the dominant goals With human uses of water and our understanding of of water resource management (Holling and Meffe ecosystems continually evolving, the solutions for meeting both ecosystem and human needs will evolve 6 URL: ͗http://www.instream¯owcouncil.org͘ over time as well. Thus, ecologically sustainable water 208 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

FIG. 1. When the natural ¯ow regime of a river is altered too greatly, it will trigger a cascade of reactions that cause the river ecosystem to simplify over time, leading to a degraded state. As a result, many human uses, native species, and other ecosystem services and products can be adversely affected. management is an iterative process in which both hu- sen et al. (1996) as springboards into the voluminous man water demands and ecosystem requirements are literature of ecosystem management. de®ned, re®ned, and modi®ed to meet human and eco- In the remainder of this paper we further discuss the system sustainability now and in the future, rather than steps included in our framework and provide examples a single, one-time solution. This implies an aggressive of their application in river systems around the world. and continual search for compatibility between eco- We also describe a case study from the Apalachicola± system and human water needs, and requires a com- Chattahoochee±Flint River basin in Alabama, Florida, mitment from all parties to ongoing participation in an and Georgia to illustrate the application of this frame- active dialogue. work to a speci®c river basin. We have developed a framework for initiating an ecologically sustainable water management program STEP 1: ESTIMATING ECOSYSTEM (Fig. 2). There are many entry points into this process, FLOW REQUIREMENTS but our experience suggests that each step is essential Water management is driven by quanti®ed objec- to achieving ecological sustainability. Similar adaptive tives, e.g., speci®ed levels of ¯ood protection, gener- water management frameworks are now being em- ation of hydropower, or reliability of water supplies ployed in South Africa (Building Block Methodology, during drought. Similarly, water-related ecological ob- King and Louw 1998) and Australia (Holistic Meth- jectives need to be quantitatively de®ned so that they odology, Arthington and Zalucki 1998), as well as in can be integrated with other water management objec- some river basins or states in the United States. In tives (Rogers and Bestbier 1997). essence, what we are describing in this paper is simply Many different aspects of hydrologic variability can the translation and application of ecosystem manage- in¯uence freshwater biota and ecosystem processes, ment principles into a water management context. In- but in constructing ecosystem ¯ow prescriptions river terested readers are referred to Walters and Holling scientists generally focus on these key components of (1990), Lee (1993), Noss and Cooperrider (1994), ¯ow regimes: wet- and dry-season base ¯ows, normal Sparks (1995), Gunderson et al. (1995), and Christen- high ¯ows, extreme drought and ¯ood conditions that February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 209

FIG. 2. A framework for ecologically sustainable water management. do not occur every year; rates of ¯ood rise and fall; ter the chances of attaining the desired ¯ow regime. and the interannual variability in each of these elements On the other hand, the ¯ow needs should be described (Arthington and Zalucki 1998, King and Louw 1998, using only as many characteristics as necessary. It is Trush et al. 2000). The particular ¯ow components or usually possible to identify a limited number of char- statistics used to de®ne ¯ow requirements in different acteristics necessary to describe ¯ow conditions of con- parts of the world necessarily vary to some degree, cern. For example, even though natural ¯oods are es- depending upon regional differences in annual hydro- sential in sustaining river ecosystems, their natural var- logic patterns. Ecosystem ¯ow requirements can be iability may not be constrained in a particular water- speci®ed as numerical ranges within which the ¯ow shed in the absence of dams. Therefore, there may be component is to be maintained (e.g., Fig. 3; Richter et no need to prescribe ¯ood ¯ow characteristics unless al. 1997b), or they can be expressed as threshold limits new dams are proposed in the future. This may help for speci®c ¯ow characteristics (Table 1, Fig. 4) that simplify the assessment of the ecological suitability of should not be crossed (Rogers and Biggs 1999, Richter various water management alternatives. Primary atten- and Richter 2000). tion should be given to ¯ow characteristics that have Generally, the greater the number of ¯ow character- been or may be altered by human in¯uences (Rogers istics used to describe ecosystem requirements, the bet- and Bestbier 1997, Rogers and Biggs 1999). 210 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

FIG. 3. Using long-term measurements of river ¯ows for the Roanoke River in North Carolina, Richter et al. (1997b) applied their ``Range of Variability Approach'' method to assess changes associated with major dam construction in 1956. Initial ecosystem ¯ow requirements for each of 32 parameters (such as annual low-¯ow duration, portrayed here) were then de®ned in terms of a range of values. For instance, one ecosystem ¯ow target was to restore low-¯ow duration (de®ned as the cumulative number of days (d) during which ¯ows are Ͻ96 m3/s) to correspond more closely to its historical range of variability. This target speci®ed that 50% of mean annual low-¯ow durations would fall within the range shown here with horizontal dashed bars; 25% would fall below this range, and 25% would fall above this range. Low-¯ow conditions are needed to dry out ¯oodplain soils to enable reproduction and growth of plants.

Estimating ecosystem ¯ow requirements requires in- in¯uenced by, or unrelated to, ¯ow variations, thereby put from an interdisciplinary group of scientists fa- obfuscating relationships between ¯ow variables and miliar with the habitat requirements of native biota population viability. Assessments of ecosystem ¯ow (i.e., species, communities) and the hydrologic, geo- requirements should not be limited to consideration of morphic, and biogeochemical processes that in¯uence species needs, however. The ¯ow needs of individual those habitats and support primary productivity and species provide only a very limited perspective of the nutrient cycling (Swales and Harris 1995, King and broader range of ¯ows needed to conserve healthy river Louw 1998; Instream Flow Council [available online; ecosystems. Of great importance is evaluating the ¯ow see footnote 6]). In South Africa, expert assessment conditions (and particularly, disturbance events asso- workshops are being convened for the purpose of de- ciated with droughts and ¯oods) that structure river and ®ning necessary ¯ows to support desired future con- ¯oodplain ecosystems (Hill et al. 1991, Richter and ditions of riverine ecosystems (King et al. 2000). Dur- Richter 2000, Trush et al. 2000). A river's natural ¯ow ing these workshops, interdisciplinary participants regime is a cornerstone for determining ecosystem ¯ow draw upon existing data, research results, ecological requirements; ecosystem ¯ow prescriptions should al- and hydrological models, and professional judgment in ways mimic natural ¯ow characteristics to the extent developing initial targets for ecosystem ¯ow require- possible (Poff et al. 1997, Tharme and King 1998). ments (King and Louw 1998). A wide variety of tools It is very important that assumptions and hypotheses and methods is being used worldwide to prescribe eco- about ¯ow±biota relationships, other non¯ow related system ¯ow requirements, and these approaches are variables that affect biota, or the in¯uence of ¯ow on evolving rapidly (Tharme 1996, Arthington and Zal- other ecosystem conditions such as water quality or ucki 1998, Bragg and Black 1999, Railsback 2001, physical habitat, be made explicit when de®ning initial Tharme, in press; Instream Flow Council [available estimates of ecosystem ¯ow requirements. Developing online; see footnote 6]). conceptual ecological models that depict presumed re- De®ning ecosystem ¯ow requirements presents lationships is an excellent way of communicating hy- many dif®cult challenges for scientists. For instance, potheses (Richter and Richter 2000). Hypotheses the link between ¯ows and the viability of a native should be formulated in a manner that allows them to species population may not be well understood, and be tested through carefully designed water management certainly not known for all populations of native riv- experiments (Step 5). These hypotheses should also, to erine species. Population viability also depends upon the extent possible, express the range of variation in a number of other ecosystem conditions that are also selected ecosystem indicators that is expected under February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 211

TABLE 1. Federal environmental agencies have de®ned ecosystem ¯ow requirements thought necessary to sustain viable populations of endangered species in the Apalachicola±Chatta- hoochee±Flint River basin in Alabama, Florida, and Georgia.

Flow parameter Guidelines based on pre-dam ¯ows Monthly 1-day minima exceed the minimum in all years exceed the 25th percentile in 3 out of 4 years exceed the median in half of the years Annual low-¯ow duration do not exceed the maximum in all years do not exceed the 75th percentile in 3 out of 4 years do not exceed the median in half of the years Monthly average ¯ow maintain the monthly mean ¯ow within the range of the 25th and 75th percentile values in half of the years Annual 1-day maxima exceed the minimum in all years exceed the 25th percentile in 3 out of 4 years exceed the median in half of the years Annual high-¯ow duration exceed the minimum in all years exceed the 25th percentile in 3 out of 4 years exceed the median in half of the years

the in¯uence of the prescribed ¯ow characteristics Inviting water managers and other interested parties (e.g., Table 2). These ecosystem indicators become part to observe the process of de®ning ecosystem ¯ow re- of the monitoring program (Step 6) that tracks the suc- quirements can have important bene®ts (J. King, per- cess of the water management plan in achieving eco- sonal communication). Water managers can help sci- logical sustainability. entists understand how to prescribe ¯ow targets in a Initial estimates of ecosystem ¯ow requirements manner that can be implemented. Water managers can should be de®ned without regard to the perceived fea- learn a lot about the possible effects of water manage- sibility of attaining them through near-term changes in ment on river ecosystems, thereby increasing their eco- water management. We reiterate our assertion that ecological literacy. Perhaps more important, water man- logical sustainability should be presumed to be attain- agers will gain insight into the nature of the uncer- able over the long run, until conclusive evidence sug- tainties in this knowledge, thereby helping them un- gests otherwise. We have been involved in numerous derstand the need for experiments and ¯exibility in water management con¯icts in which initial percep- water management. It is important for water managers, tions of unfeasibility were overcome through creativity conservationists, and water users to understand that and deeper analysis, or a change in the socioeconomic scientists will not be able to provide comprehensive or political landscapes that made possible what had and exact estimates of the ¯ows required by particular seemed impossible a decade or two earlier. species, aquatic and riparian communities, or the whole

FIG. 4. One of the ecosystem ¯ow requirements identi®ed for the Apalachicola River in Florida is to maintain daily ¯ows above targeted minimum levels during each month of the year. Ecosystem ¯ow requirements (thin line) are compared with model simulated daily ¯ows (thick line) for the drought year of 1985. River ¯ow is in cubic meters per second (m3/s). 212 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

TABLE 2. Examples of ecosystem indicators being used in managing river ecosystems within Kruger National Park in South Africa.

Ecosystem Unit of Measurement Measurement Sampling Threshold of possible attribute measurement frequency area method concern (m3/s) River ¯ow Base¯ow in cubic meters per continuous speci®ed river stream¯ow gauge 2.0±4.0 Sabie River second (m3/s) reaches during drought Higher ¯ows cubic meters per continuous speci®ed river stream¯ow gauge 5.0±8.0 in Sabie second (m3/s) reaches River during drought Geomorphic Channel types proportion of every 5 years and 100±1000 m of aerial photos depends on chan- channel type after 25ϩ year river reach nel type² found in reach ¯oods Vegetation Population size class frequen- every 3 years and representative transects: stem di- must show recruit- structure of cy distribution after 25ϩ year stream reaches ameter of indi- ment of riparian key species ¯oods viduals species every 10 years or less Fish Distribution of percentage of sites 3±5 year intervals 6 sites/river seine netting or 50% loss of range individual occupied by electroshocking of individual species each species species Frequency of 3±5 year intervals 6 sites/river measure a mini- occurrence of a ®sh length unitless mum of 150 in- range of sizes, dividuals per including both species juveniles and adults Invertebrates total number of twice/year (March 5 sites/river bottom-layered ag- 50% change in invertebrates and April) itation and abundance in contribution per sweep netting each taxa taxon to total (mud, gravel); number kick and sweep netting (stones) and net sweeps of river margin vegetation Birds By habitat presence or ab- every summer 20 ϫ 100 m tran- auditory and when any catego- types (reed sence of a rep- sects walked visual ry is no longer beds, mud resentative spe- along river bank represented ¯ats, and cies others) By functional presence or ab- every summer 20 ϫ 100 m tran- auditory and when any catego- representa- sence of a rep- sects walked visual ry is no longer tives (e.g., resentative spe- along river bank represented frugivore, cies granivore, and others) Water quality Ammonium every two weeks at speci®c sam- collect water sam- 0.1 mg/L pling points ples; phenate hypochlorite method pH every two weeks at speci®c sam- collect water sam- 6.5±8.1 pling points ples; pH meter Water tempera- every two weeks at speci®c sam- in situ over 24-h 8±25ЊC ture pling points period using thermometer Note: This is only a partial listing of indicators being used by park managers; for full list see Rogers and Bestbier (1997). ² In pool±rapid channel types, lateral and point bars must be 20%, and pools need to be 15% or more of total area. In anastamosing channel types, bedrock core bars must be 50% or more; other key units must be 2±10% of area. February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 213

FIG. 5. A hydrologic simulation model developed for the Apalachicola±Chattahoochee±Flint (ACF) River basin enabled negotiators to assess the in¯uence of projected increases in human water uses and proposed dam operations on the ¯ow regime of the Apalachicola River in Florida. Fifty-®ve years of simulated daily ¯ows were generated. One of the ecosystem ¯ow requirements for the Apalachicola River speci®es that critically low ¯ows (Ͻ155 m3/s) should not occur more than 24 d in any year. Modeling results suggest that incompatibilities between human demands and this ecosystem ¯ow requirement would occur in 6 of the 55 yr under the January 2002 Florida proposal (gray bars). This ecosystem ¯ow requirement was exceeded in four years under historical ¯ow conditions (black bars). river ecosystem. Rather, scientists should be able to steps. Daily ¯ow hydrographs resulting from various provide initial estimates of ecosystem ¯ow require- levels and types of human use can be generated for ments that need to be subsequently tested and re®ned, particular locations, enabling both visual and statistical as described later. comparisons between ¯ows required for ecosystem support and human-altered ¯ows (Figs. 5 and 6). STEP 2: DETERMINING HUMAN INFLUENCES ON THE FLOW REGIME STEP 3: IDENTIFYING INCOMPATIBILITIES BETWEEN Humans use water for myriad purposes including mu- HUMAN AND ECOSYSTEM NEEDS nicipal and industrial water supply, agricultural irriga- Areas of potential incompatibility in water manage- tion, hydroelectric power generation, waste assimilation, ment can be identi®ed by comparing ecosystem ¯ow navigation, and recreation. These human uses necessar- requirements (Step 1) with the ¯ow regime resulting ily modify the natural ¯ow of rivers. Assessments of the from meeting human needs (Step 2). These areas of nature, degree, and location of human in¯uences on nat- incompatibility become the point of origin for discus- ural ¯ow regimes should be performed for both current sions in Step 4 (e.g., Figs. 5 and 6). When these in- and projected levels of human use, and expressed in compatibilities between human needs and ecosystem spatial and temporal terms that are consistent with the requirements are well de®ned, efforts can be most ef- de®nition of ecosystem ¯ow requirements. fectively focused toward resolving them. Hydrologic simulation modeling has advanced rapidly Areas of potential incompatibility must be examined and computerized models have become essential tools both within and among years. Within-year evaluations for understanding human in¯uences on river ¯ows and will reveal the speci®c months or seasons during which designing ecologically sustainable water management ecosystem ¯ow requirements are likely not to be met. approaches. Such models are capable of performing si- Evaluations of multiple years will facilitate understand- multaneous calculations of all the many in¯uences on ing of the frequency with which ecosystem require- water ¯ows, even in complex river systems. They can ments could be violated (Fig. 5). Areas of potential be used to evaluate river ¯ow changes expected under incompatibility between human and ecosystem needs proposed water management approaches, such as in- should also be evaluated for each river reach of con- creased future human demands and associated operation cern, as the nature and degree of con¯ict can vary of water infrastructure. Because short-term hydrologic widely from upstream to downstream, or across a wa- conditions such as extreme low ¯ows or ¯oods can have tershed. Using models to explore water management tremendous ecological in¯uence, it is highly desirable alternatives can identify discrete pinch points and high- and increasingly feasible to develop hydrologic simu- light the marginal differences between alternatives, lation models that operate on daily (or shorter) time thereby constraining the scope of the con¯ict (Carver 214 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

FIG. 6. Simulated natural ¯ows during 1985 (black line) for the Apalachicola River are compared with ¯ows that would occur under proposed future (2030) human demands and dam operations (gray line), as prescribed in the January 2002 Florida proposal. This comparison suggests that the river's natural ¯ow variability can be protected to a high degree under projected development conditions. et al. 1996). Statistical assessment of the differences speci®c management goals that give better de®nition between human-in¯uenced ¯ow conditions and eco- to the vision, and is ultimately underpinned by a set of system requirements can help quantify the magnitude speci®c, quanti®ed objectives (expressed as ``thresh- of potential con¯icts (Richter et al. 1996). olds of possible concern'' in Table 2), which provide When human-in¯uenced ¯ow regimes are found to managers with management targets. Quanti®ed objec- be incompatible with ecosystem ¯ow requirements (ei- tives can include proposed levels of hydropower gen- ther presently or in the future), water managers, sci- eration, delivery of water supplies, management of res- entists, water users, and conservationists will need to ervoir lake levels, and other human interests as well seek ways of alleviating the con¯icts, as discussed in as ecosystem targets. the next step. In this step of our framework, stakeholders negotiate to have their desires or needs expressed in the set of STEP 4: COLLABORATIVELY SEARCHING mutually agreeable goals that will drive water man- FOR SOLUTIONS agement activities. We believe that ecologically sus- Once the areas of potential incompatibility have been tainable water management ultimately depends upon well de®ned and bounded in space and time as de- mutual commitment to a basic philosophy that no one scribed previously, options for reducing or eliminating wins unless everyone wins; conservationists must con¯icts between human and ecosystem needs can be strive to meet human needs while water managers com- explored in an open dialogue among stakeholders. Fos- mit to meeting ecosystem requirements. When all par- tering a collaborative dialogue among those affected ties are engaged in working toward ecologically sus- by water management decisions will help clarify val- tainable water management, the power of human in- ues, share information, and build trust between partic- genuity can be optimally directed. ipants, making it far easier to build the consensus need- During the formulation of mutually agreeable goals, ed to develop and implement ecologically sustainable some of the incompatibilities identi®ed in Step 3 will water management (Bingham 1986, Howitt 1992, Ax- likely be resolved. For instance, certain water users elrod 1994, Rogers and Bestbier 1997). may decide that they can achieve adequately satisfying Human needs, desires, and preferences, including bene®ts while modifying their current water use or fu- those pertaining to river ecosystem protection or res- ture expectations. On the Roanoke River in North Car- toration, should be expressed as a set of goals that olina, The Nature Conservancy has proposed modi®- collectively represent stakeholder interests. This set of cations to hydropower dam operations to alleviate un- goals represents the desired integration of human and naturally long ¯oods during the growing season that ecosystem needs. Rogers and Bestbier (1997) suggest impact ¯oodplain ecosystems. The proposed modi®- a framework called an ``objectives hierarchy'' for such cations are expected to result in hydropower generation goal setting. This objectives hierarchy begins with for- losses of only ϳ2±5%. The dam operators have indi- mulation of a broad management vision, includes more cated that this level of reduction is probably acceptable. February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 215

Box 1. Green River, Kentucky Scientists from The Nature Conservancy are now working with the U.S. Army Corps of Engineers to design modi®cations to dam operations on the Green River in Kentucky to reduce their impact on natural ¯ow conditions and aquatic species. One of the richest assemblages of native ®sh and mussels in North America is located downstream of the Green River Dam, operated by the Corps since 1963 to provide ¯ood control and reservoir-based recreational bene®ts. Substantial alterations to the river's natural ¯ow regime occur each year in the fall, when the Corps switches from recreation lake management to ¯ood control operations. Reservoir levels are maintained at a high level during summer to accommodate recreational uses. During September and October, the water level in the reservoir is quickly lowered by Ͼ3 m to restore storage capacity needed to capture winter ¯oods. Releasing this large volume of water in a short period of time produces greatly elevated ¯ows that extend far downstream from the dam and disrupt native biota. Aquatic scientists hypothesize that steady low ¯ows are needed in the fall season to concentrate certain prey species, enabling their predators to feed more ef®ciently. Certain mussels are believed to release larvae during the autumn season, which may be disrupted by high ¯ows. Other aquatic organisms likely depend upon naturally quiescent, low-¯ow periods for conserving energy prior to winter. The collaborative efforts between the Corps and the Conservancy are focused on shifting the timing of lake level lowering (and associated increases in downstream river ¯ows) from September±October to late November, when river ¯ows would be naturally higher during the onset of the winter rainy season. Because the lowering of reservoir levels will also be conducted over an extended period, the daily reservoir releases can be lessened. In addition to shifting the timing and increasing the duration of the reservoir draw-down, the dam releases will be pulsed to coincide with storm events rather than releasing at a constant rate, thereby mimicking some of the river's natural patterns of variability. The basic ideas behind these operational changes were identi®ed during an initial two-hour discussion between the scientists and engineers. This dialogue moved quickly toward possible solutions because the areas of potential incompatibility had been well described by Conservancy scientists; Corps engineers shared the Conservancy's goal of maintaining the river ecosystem in a healthy condition; and they both sought to restore ecological integrity while continuing to meet the operational purposes of the dam.

Equipped with adequate data and shared means for servation in cities, industries, and agriculture are reassessing them, water managers, scientists, conserva- ducing the volume of water needed to support human tionists, and water users should carefully examine each endeavors, or eliminating the need to build additional area of potential incompatibility identi®ed in Step 3 storage reservoirs that might further impair natural hy- and consider whether each ecosystem requirement and drologic regimes (Maddaus 1987, Postel 1999, Gleick human use might be met in alternative ways that would 2000, Vickers 2001). Many governmental entities are remove or reduce the con¯ict. Some of the most pow- adopting demand management strategies that place lim- erful means of resolving these con¯icts involve chang- its on the amount of allowable water withdrawals from ing the timing or location of human uses toward greater certain freshwater sources. Water market transactions, compatibility with natural hydrologic cycles or the sea- including the purchase of irrigation water rights and sonal or life cycle needs of native species. For instance, their conversion to ``instream ¯ow rights'' that allow can water be captured for human use during a time of the water to remain in the river (Gillilan and Brown the year that minimizes the relative change to the nat- 1997), or paying farmers not to irrigate ®elds during ural hydrograph and its ecological consequences? Can drought periods, hold promise for keeping river ¯ows the location of a water diversion be relocated down- from dropping to critically low levels (Michelsen and stream of critical ®sh spawning areas? Young 1993, Wigington 2000). As new strategies suc- A growing number of innovative strategies are now ceed and begin to be more widely communicated to being tested and put to use for the purpose of elimi- water managers and conservationists, we expect the nating con¯icts between human and ecosystem needs probabilities for attaining ecologically sustainable wa- for water (see Boxes 1 and 2 for Green River, Kentucky ter management in the world's river basins to improve and San Pedro River, Arizona). Dam operations are considerably. being modi®ed to reshape human-in¯uenced hydrographs into something more compatible with ecosystem STEP 5: CONDUCTING WATER requirements while still meeting the human needs for MANAGEMENT EXPERIMENTS which they were originally designed (Natural Resourc- During each of the preceding steps, a number of es Law Center 1996). New technologies for water con- uncertainties about ecosystem ¯ow requirements or hu- 216 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

Box 2. San Pedro River, Arizona In the upper San Pedro River basin of southern Arizona, water managers and conservationists argued for more than a decade about the causes of measured declines in river base ¯ows and the degree to which continued groundwater pumping for municipal and agricultural use might affect the river in the future (Commission on Environmental Cooperation 1999). In 1998, under the leadership of the Arizona De- partment of Water Resources, representatives from federal and state agencies, municipal governments, and conservation organizations agreed to step back from this debate and work together on a plan to meet both human and ecosystem water demands over the long run (Upper San Pedro River Partnership 1998). They formed the Upper San Pedro Partnership to seek consensus-based ideas for reducing human impacts, for organizing ecological research to examine more rigorously the water needs of the riparian ecosystem along the river, and for reassessing the groundwater models that have been developed by various parties. The partnership has collaborated on an ambitious work plan including a variety of water conservation activities, recharge of treated wastewater ef¯uent, and retirement of water-consumptive agriculture. The partnership committed more than $18 ϫ 106 (U.S. dollars) to the effort during the ®rst two years. In this case, Step 4 of the framework (Fig. 2) was predicated on reiteration of Steps 1±3, and the Upper San Pedro Partnership is an important example of revisiting and possibly modifying ecosystem ¯ow requirements. The willingness of the major stakeholders to reexamine both human water needs and ecosystem ¯ow requirements in a collaborative setting was an important breakthrough. This example illustrates the fact that the time frames required for developing an ecologically sustainable water management plan can take decades. The example from the Green River in Kentucky (see Box 1) suggests that quick progress is sometimes possible and always desirable, but hardly assured.

man uses will likely have arisen. Even when attempts periments can back®re by introducing additional con- to resolve incompatibilities are pursued collaboratively fusion about cause and effect, and result in increased and earnestly, water managers may remain uncertain frustration that can badly damage collaborative efforts. about the feasibility of speci®c proposed modi®cations The action plan developed by the Upper San Pedro to water management, or river scientists will be un- Partnership (see Box 2 for San Pedro River, Arizona) certain about expected ecological responses. includes a number of water management experiments Unfortunately, these uncertainties commonly cause designed to reduce human impacts on groundwater a breakdown in collaborative dialogue. When water ¯ows. For instance, wastewater from the City of Sierra managers, scientists, water users, and conservationists Vista will now be injected back into the groundwater are asked to ``cut a deal'' in the presence of substantial aquifer rather than continuing to release it into evap- uncertainty, one or more parties may balk, thus delay- orative ponds. Also, water conservation measures are ing or terminating the search for compatible solutions. being implemented by various municipalities and a mil- However, by instead framing critical uncertainties as itary base. The hydrologic improvements associated hypotheses that can be tested and resolved through wa- with these water management experiments have been ter management experiments, paralysis may be avoid- modeled using groundwater simulation models, but ed. verifying their actual bene®ts will require careful mon- Water management experiments must be carefully itoring. If these experiments suggest that less actual designed and executed if they are to yield the desired bene®t is attained than expected, the partnership will reduction of uncertainty, however. It is essential that need to identify additional measures or broader appli- scienti®cally credible experimental designs be em- cation of their measures to realize success. ployed to the extent feasible. If the experiment is not intended to last for many years, the selected response STEP 6: DESIGNING AND IMPLEMENTING AN variables should be adequately sensitive to enable de- ADAPTIVE WATER MANAGEMENT PLAN tection of response during the term of the experiment. The last step of our framework should never be com- Most important is the formulation of testable hypoth- pleted; to be ecologically sustainable, water manage- eses based upon conceptual models of the expected ment should be perpetually informed by monitoring, response of the hydrologic and ecological systems to carefully targeted research, and further experimenta- the water management experiments (Richter and Rich- tion to address new uncertainties or surprises, and man- ter 2000). These experiments must be carefully mea- agement approaches must be continually modi®ed in sured or monitored. And of course, adequate ®nancial light of increased understanding or changes in human support must be provided. Without appropriate design, and ecosystem conditions. While much has been writ- evaluation, and funding, such water management ex- ten about adaptive ecosystem management, we want to February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 217 emphasize a few elements particularly relevant to water vision of instream ¯ows below private hydropower management. dams in the United States are commonly speci®ed in 40-yr dam operating licenses, making modi®cations to Monitoring program these ¯ow requirements costly, time-consuming, or le- During the initial determination of ecosystem ¯ow gally problematic. The design of water infrastructure, requirements, a number of hypotheses will be generated such as water release structures at dams, or pipes and concerning the expected responses of various ecosys- pumps used to divert water from a river, can place tem conditions to the ecosystem ¯ow prescription. For serious constraints on management ¯exibility if these example, it might be hypothesized that under the pre- structures are not designed to pass variable volumes of scribed ¯ood conditions, the population of a target ®sh water. species will ¯uctuate within an estimated range. Some It is absolutely essential that an ecologically sus- of the most important hypotheses will be tested during tainable water management plan preserves the ability the water management experimentation described for to respond to new information gained from water man- Step 5 of our framework. Other hypotheses should be agement experiments or a long-term monitoring pro- tested through the collection and analysis of monitoring gram, and to alter the plan and related infrastructure data over longer time frames. Monitoring data should operations accordingly. This ultimately depends on the be collected for a suite of ecosystem indicators that ¯exibility of water management infrastructure, regu- re¯ect ecological integrity as a whole (Noss 1990), in latory or legal mechanisms controlling water use, and a manner that allows for testing hypotheses developed the political will to stay with an ever-evolving process. in earlier steps. Over the long term, managing adaptively to meet the In Kruger National Park in South Africa, ecosystem goal of ecologically sustainable water management will ¯ow requirements and targeted ranges for other eco- increase certainty as the most troublesome uncertain- system indicators have been de®ned for geomorphic ties are resolved, infrastructure operations are re®ned conditions, vegetation, ®sh, invertebrates, birds, and for greater ef®ciency and compatibility, and ecological water quality (Table 2; Rogers and Bestbier 1997). For degradation halted. As adjustments in the status quo each ecosystem attribute, scientists have speci®ed the are required, parties may need to seriously explore frequency, scale, and methods for measurement, as well ways to share and minimize the ®nancial and economic as an associated threshold of possible concern. These impacts, including the possibility of indemni®cation thresholds are expressed as upper or lower values, pro- agreements that cover some of the costs associated with viding bounds within which an ecosystem attribute is these changes. If it is impossible to implement new or expected to ¯uctuate, or thresholds that should not be modi®ed water management strategies over time, the crossed. options for attaining ecologically sustainable water Selecting a suite of indicators and de®ning targeted management will be diminished greatly. ranges of variation or critical thresholds for each attribute requires a high level of understanding of the Governance interaction among river ¯ows, human activities, and Water managers will need to continually respond to ecosystem response. As results from the monitoring new information by modifying their ecologically sus- program clarify these relationships, new ecosystem in- tainable water management plan. The process and au- dicators or target ranges may need to be selected. thorities for such decision-making must be clearly ar- ticulated in the plan. We strongly recommend that this Adaptability governance include the formation of a scienti®c peer As described in Step 4, adaptive management should review committee, chartered with responsibility for re- always begin with de®ning mutually acceptable goals viewing the design and results of water management for water management (Rogers and Bestbier 1997). Def- experiments and monitoring and making recommen- inition of mutually acceptable goals related to ecosys- dations to a river basin commission or other local or tem health, economic bene®ts, and other societal needs regional management agency with ultimate decision- and preferences should be an explicit product of the making authority. collaboration we encourage in Step 4. Water management activities can then be directed at trying to fully Secure funding attain these goals. This may require numerous itera- The management plan should also identify funding tions or trials, such as making modi®cations to dam needs and sources, with an emphasis on sources that operating rules or water withdrawal schedules. It may can provide for long-term security. Even short-term also become necessary to revisit mutually agreed upon breaks in funding support can severely impact water goals if the full suite cannot be realistically attained. management experiments and monitoring programs. Unfortunately, traditional water management plans The success of monitoring programs relies upon con- have commonly been formulated in ways that make tinuous, consistent measurements adequate to capture them dif®cult, if not impossible, to modify frequently short-term and interannual ¯uctuations in ¯ow and eco- or quickly. For example, speci®c requirements for pro- system conditions. Multiple-year congressional appro- 218 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

FIG. 7. The Apalachicola±Chattahoochee±Flint (ACF) River basin. priations, such as those presently supporting the Long Rivers and their tributaries drain an area of Ͼ50 000 Term Resource Monitoring Program in the Upper Mis- km2, reaching from the southern Blue Ridge Mountains sissippi River basin can provide some degree of ®nan- to the Gulf of Mexico (Fig. 7). The Chattahoochee cial assurance. Tying funding sources to reliable rev- River begins north of Atlanta, passes through the city enues such as water user fees or hydropower revenues and then forms the border between Georgia and Ala- generated at public facilities may provide greater de- bama. It meets the Flint River, which begins just south pendability. of Atlanta and ¯ows through southwest Georgia, at the Both the Grand Canyon Monitoring and Research Florida border. From this con¯uence, the Apalachicola Center and the monitoring element for the Recovery River meanders 150 km through the Florida panhandle, Implementation Program for Endangered Fish Species emptying into the Gulf of Mexico at Apalachicola Bay. in the Upper Colorado River Basin are supported by The Apalachicola±Chattahoochee±Flint (ACF) River hydropower revenues generated at the main dams of basin has long been noted for its freshwater biodiver- the Colorado River Storage Project. This annual fund- sity, including aquatic communities of endemic and ing is capped but is authorized to continue as long as imperiled species, anadromous and sport ®sh. The Ap- the monitoring is scienti®cally and politically justi®ed. alachicola River and surrounding lands in the heart of APALACHICOLA RIVER CASE STUDY the Florida panhandle was reported in Stein et al. Lying within the states of Georgia, Alabama, and (2000) as home of one of the nation's highest concen- Florida, the Chattahoochee, Flint, and Apalachicola trations of imperiled species. The State of Florida has February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 219 acquired much of the river's broad ¯oodplain and man- resents an historical opportunity to establish a prece- ages it for conservation purposes. The Apalachicola dent for the future of water management in the eastern Bay is considered to be one of the most productive United States and to coordinate river basin management estuaries in North America and is valued for its oysters, among the three states. shrimp, blue crabs, and ®sh species including striped Discussions during the water allocation negotiations bass, sturgeon, grouper, drum, and ¯ounder. revealed the interests of each of the states. Simply stat- The water resources of the ACF basin were sub- ed, Georgia's primary concerns are to secure adequate stantially developed in the 20th century for human water supply for M and I and agricultural uses such uses. Sixteen dams were built on the Chattahoochee that economic growth is not constrained, and maintain and Flint Rivers. Five of these dams are federal projects high reservoir levels for recreational use. Alabama pri- operated by the Army Corps of Engineers for hydro- marily wishes to protect suf®cient quantity and quality electric power, navigation, recreation, ®sh and wildlife, of water for water supply and waste assimilation in the water supply, and ¯ood control. Surface and ground- mid-Chattahoochee, and Florida desires to sustain a water withdrawals are made for municipal and indus- ¯ow regime that will maintain the biological diversity trial (M and I) water supply and for irrigated agricul- and productivity of the Apalachicola River and Bay. ture. Dramatic increases in water use have resulted Other stakeholders reinforced these values, and added from extreme population growth in the metropolitan hydropower, navigation, maintenance of stable lake Atlanta area, a mid-century population of 500 000 grew levels, recreation, endangered, sport, and commercial to Ͼ4 million (4 ϫ 106) by 2000, and increased reliance species, and water quality protection to the list of con- on irrigation for agriculture in southwest Georgia. cerns. From 1970 to 1990 surface water withdrawals in- While negotiations continue as of this writing, we creased by 29% and groundwater withdrawals, pri- have used the states' proposals of January 2002 as the marily for agriculture, increased by 240% (ACOE basis for our case study assessment. Many of the key 1998). elements of our framework for ecologically sustainable To address the Atlanta region's growing water needs, water management are addressed by these proposals. the state of Georgia asked the Corps to reallocate water In particular, we focus on the Florida proposal, which storage in the upstream federal reservoir (Lake Lanier) we feel best addresses our key elements. from hydropower generation purposes to provision of water supply, to which the Corps consented. In 1990, Ecosystem ¯ow requirements Alabama's concern about the potential downstream im- Several studies were conducted as part of the Com- pacts of this reallocation led them to ®le a lawsuit prehensive Study to develop a better understanding of against the Corps. When Florida and Georgia ®led to relationships between ¯ow levels and habitat condi- intervene in the suit, the states made an important de- tions in the ACF basin (Chanton 1997, Freeman et al. cision to seek a negotiated settlement that would avoid 1997, Huang and Jones 1997, Iverson et al. 1997, Lewis litigation. Importantly, they agreed that water alloca- 1997a, b, Light et al. 1998). Subsequent to these stud- tion in the whole ACF basin should be negotiated rather ies, two federal agencies reviewed historical records of than to argue about the use of any single reservoir. river ¯ow and native species surveys to develop a set They agreed to conduct a Comprehensive Study to pro- of ``instream ¯ow guidelines'' (Table 1) (USFWS and vide factual information on water availability, forecast USEPA 1999). These guidelines address intra- and in- water needs, and explore options to meet them. Con- terannual ¯ow variability by setting threshold limits tinued discussions between the states led to the signing for the monthly one-day minimum, annual low-¯ow of the interstate Apalachicola±Chattahoochee±Flint duration, annual one-day maximum, and annual high- River Basin Compact in 1997. ¯ow duration that must be met in all years, in three The compact provides a framework for the states, out of four years or in two out of four years; and as a with the approval of the federal government, ``to de- range of values for the monthly average ¯ows. Nu- velop a water allocation formula for equitably appor- merical values for the speci®ed parameters have been tioning the surface waters of the ACF Basin among the de®ned for speci®c locations on each of the three rivers. states while protecting the water quality, ecology and In essence, these guidelines represent an initial ar- biodiversity of the ACF'' (U.S. Congress 1997). The ticulation of ecosystem ¯ow requirements to support compact formed an ACF Commission made up of the biodiversity in the basin and have enabled federal en- governors of the three states and a federal commis- vironmental agencies and others to assess the possible sioner appointed by the President of the United States. impact of any proposed water allocation formula on Once the three governors agree upon an allocation for- the ecological integrity of the ACF basin. The guide- mula, the federal commissioner must concur or not con- lines focus on a small subset of ecologically relevant cur, based on compliance with federal laws. Negotia- hydrologic parameters that could be substantially af- tions over the water allocation formula began in 1998 fected by water management in the ACF basin, and and continue as of April 2002. This compact is the ®rst thus have been useful in drawing attention to some key in the ``water rich'' southeastern United States. It rep- hydrologic parameters in the negotiations. However, 220 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1 these ¯ow guidelines have not received much attention ervoir operations, and other water management issues. from the states and their proposals have not addressed In turn, the output of these model runs by the states them in any explicit way. This neglect can be largely has been analyzed by the federal environmental agen- explained by the reluctance of the negotiators to use cies to assess incompatibilities with their instream ¯ow ¯ow targets that they felt had not been adequately guidelines. linked to desired ¯oodplain or channel conditions and There has been disagreement over some of the key ecological responses. While the federal ¯ow guidelines inputs to these models, including the relationship be- were supported with a narrative that described the gen- tween groundwater pumping and river ¯ows, irrigation eral importance of the speci®ed ¯ow conditions for demands, and other water use projections. Tremendous sustaining species and ecosystem health, the numerical effort was expended in assembling a common set of targets were based primarily on statistical character- input data for the hydrologic models, but some key ization of the historical ¯ow regime because the federal inputs such as irrigation water consumption during agencies hoped to preserve as much of the historical droughts was very dif®cult to estimate due to lack of ¯ow conditions as possible. The negotiators wanted to monitoring data. The lack of agreement on model input better understand how a ¯ow of a particular level would has been an obstacle in the negotiations, because it has ®ll the channel, inundate the ¯oodplain, or otherwise made comparisons of the states' proposals dif®cult. affect biota in particular reaches. Fortunately, work conducted during the Comprehen- Areas of incompatibility sive Study did provide information about instream hab- While the ACF basin lies within the comparatively itat availability in the Apalachicola River at various water-rich Southeast, periodic episodes of drought, of- low-¯ow levels, and identi®ed high-¯ow levels at ten lasting for multiple years, do occur. During a which ®sh gain access to secondary channels and back- drought from 1999 to 2001 the annual ¯ows in the river water areas in the ¯oodplain (Freeman et al. 1997, Light were only 40% of average. Such periods of drought et al. 1998). The Florida negotiators relied heavily upon have become the nexus of con¯ict between human and these limited studies in framing their water allocation ecosystem needs for water. For example, maintaining proposal, while also trying to protect as much of the high reservoir levels for recreation and preserving wa- natural ¯ow regime as possible (S. Leitman, personal ter storage during droughts con¯icts with needed re- communication). leases for water quality, hydropower, navigation, and We believe the lack of adoption of any form of con- ecosystem ¯ows. These con¯icts are most acute during sensus-derived ecosystem ¯ow requirements greatly the summer, when naturally low river ¯ows are depleted hindered the ACF basin negotiations. Before any set by various human uses. In the negotiations, suggestions of ¯ow guidelines can be fully employed in the fashion were made to curtail or constrain certain uses to enable suggested by Steps 1±3 of our framework, the states other uses to be met adequately. and federal agencies must reach consensus on ecosys- The federal instream ¯ow guidelines include two tem ¯ow requirements. One way to facilitate such con- low-¯ow parameters (Table 1): a limit on the one-day sensus might be to convene a more formal and rigorous minimum ¯ow in each month and a limit on the max- scienti®c assessment of ecosystem ¯ow requirements, imum number of days in each year that ¯ows can be engaging multidisciplinary academic and agency sci- below a certain threshold. The water allocation agree- entists from each of the three states and beyond. An ment fails to meet these low-¯ow guidelines in some excellent model for such structured assessment is the years (Fig. 5). Therefore, the ecological sustainability Building Block Methodology being employed in South of this water allocation remains in question. Africa (King and Louw 1998). The search for solutions Evaluating human in¯uences The original deadline for arriving at an acceptable The Comprehensive Study produced estimates of ex- allocation formula was set by the Compact for 31 De- isting and projected water demands for M and I, ag- cember 1998, but the deadline was extended more than ricultural, and other uses. Subsequently, hydrologic 10 times. The states are highly motivated to achieve a simulation models were developed to enable assess- negotiated agreement; the alternative is to resolve the ment of daily ¯ow regimes at 14 different locations in issue in the U.S. Supreme Court. The water allocation the basin. Alternate water management scenarios can proposals submitted by each of the states have provided be explored by modifying projected water demands and the basis for the negotiations. The hydrologic models reservoir operations in the models. and analyses of their outputs have proved to be valuable Each of the three states has used these hydrologic tools for developing, communicating, and assessing a models in developing their water allocation proposals variety of water management alternatives. Stakeholder for consideration by the other states and federal rep- meetings, technical meetings, and workshops and other resentatives. Each state has modi®ed the model(s) to private meetings have been conducted both inside and re¯ect key elements of their respective proposals, e.g., outside of the formal negotiations. Each of these venues projected growth in water consumption, proposed res- offered an opportunity to share information, present February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 221 concerns or preferences, and collaborate in a search for operations and groundwater management in the Flint solutions. River basin, are ideally suited for experimentation. Steps 1 and 2 of our framework directly address two The Army Corps of Engineers is beginning an as- of the biggest obstacles encountered in the ACF basin sessment of needed modi®cations in its ``Water Control negotiations: lack of agreement on ecosystem ¯ow re- Plan'' for the major reservoirs in the ACF basin. Rather quirements and the implied limits on human uses re- than attempting to develop a long-term plan of oper- sulting from these, and lack of agreement on current ations at this time, the Corps could instead design its and projected water uses. Without well-de®ned, agreed operating plans as short-term (i.e., 5±10 yr) experi- upon quanti®cation of ecosystem ¯ow requirements ments. Such experiments would test the plan's ability and human uses, each party evaluated the potential in- to help meet ecosystem ¯ow requirements while keep- compatibilities differently. This limited the ability to ing other performance indicators, including lake level focus a creative search for solutions. ¯uctuations and hydropower generation, within target- In the absence of agreement on ecosystem ¯ow reed ranges. quirements and water use projections, the states con- The Flint River Drought Protection Act of 2000 structed proposals that focused on the desired net ¯ows might offer a viable solution to reduce agricultural wa- (and associated recurrence intervals) at selected places ter use in certain years and thereby enable the ecosys- in the basin. For instance, the Florida negotiators fo- tem ¯ow requirements to be met during droughts. This cused on framing the water allocation formula in a act authorizes payments from the state of Georgia to manner that would minimally impair the natural ¯ow farmers that curtail irrigation on selected areas when regime of the Apalachicola River, and in this effort the EPD declares a drought by 1 March. Each drought they were quite successful (Fig. 6). Their proposal in- period can be viewed as an experiment to test the state's cludes a cap on total water withdrawals from the Chat- ability to reduce water use to the level that Flint River tahoochee River in the Atlanta area, and it dictates how and state line ¯ow requirements can be attained. If each much water must be released from the reservoirs for such experiment is designed and evaluated carefully, downstream ecosystem support according to weekly water managers will be able to determine the amount reservoir storage levels. The Florida proposal also in- of irrigation compatible with ecosystem ¯ow require- cludes some important commitments to adaptive man- ments during drought. agement (see Apalachicola River: Adaptive management). Adaptive management Because of uncertainties in both future water de- Water management experiments mands and ecosystem ¯ow requirements, it is highly While millions of dollars and many years of effort inadvisable to make any water allocation formula im- have gone into developing a set of data and tools for mutable. Numerous parties throughout the negotiations building the water allocation formula, there remain have advocated for managing the ACF basin adaptively some areas of uncertainty that have frustrated the and including provisions in the allocation formula states' efforts to reach agreement. These uncertainties agreement to address it. The states' proposals include include the amount of water presently being used as some key elements of adaptive management. well as projected water uses; the effects of alternative 1. Governance.ÐThe Florida proposal calls for cre- reservoir operating plans on lake levels, hydropower ating a Scienti®c Advisory Panel that will recommend generation, ®sheries, and navigation; potential respons- a set of ecosystem performance indicators and a pro- es of the river ecosystem and individual species of gram for evaluating whether they are being maintained concern to alterations in the ¯ow regime; and physical in satisfactory condition. The Scienti®c Advisory Panel relationships between groundwater levels, agricultural will also be responsible for recommending modi®ca- pumping, and river ¯ows in the Flint River basin, which tions to the monitoring program as needed. Addition- strongly affects Georgia's ability to meet ¯ow targets ally, an ACF Committee will include representatives in the Apalachicola River at the Florida state line dur- from the states and federal agencies. The committee ing droughts. will oversee monitoring of all ecosystem performance Some of these uncertainties can be addressed with indicators, create an electronic database available to additional investment in data gathering or short-term the public, and make recommendations for needed research. For example, the Georgia Environmental Pro- technical studies or additional data collection. tection Department (EPD) is conducting a ``Sound Sci- 2. Adaptability.ÐThe state proposals include no ence Study'' in the Flint River basin to further under- speci®c mechanism for modifying the interstate ¯ow standing of the groundwater/surface water relation- allocation formula or re®ning water management based ships. Other uncertainties, including growth in future on results of the monitoring program. However, the water demands and ecological responses to water man- Florida proposal calls for the issuance of a performance agement, are best addressed through design and im- report to the public before the 10th and 25th anniver- plementation of an adaptive management plan, dis- saries of the agreement. After conducting public hear- cussed next. Two major areas of uncertainty, reservoir ings on these reports, the ACF Commission is to pub- 222 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1 lish a ®nal report. Presumably, this formal public re- greater effort should have been expended in designing view process and annual reports and recommendations a way to meet both these ecological goals as well as from the Scienti®c Advisory Panel could cause the other mutually agreed upon goals for meeting various ACF Commissioners to revise the allocation formula human uses. This realization strongly shaped the frame- or water management practices as needed to meet the work we outline in this paper, in which the ®rst step intent of the ACF compact. is estimating ecosystem ¯ow requirements. This en- 3. Secure funding for monitoring.ÐWhile funding ables water planners and managers to give due consid- has not been addressed explicitly in the state proposals, eration of ecological requirements throughout the plan- the Florida proposal does ®rmly commit to monitoring ning or negotiating process. the performance indicators. Success of the monitoring Several existing water policies explicitly call for in- program will be dependent upon secure funding from clusion of ecological goals. Florida's Water Resources state and federal governments or water users that will Act of 1972 called for the state to set ecosystem ¯ow ensure long-term continuity. requirements, in the form of minimum ¯ows and lake The ACF basin is an important example of the pro- levels, within each of their water management districts. gress being made around the world in ecologically sus- Permitting of water withdrawals is intended to avoid tainable water management. It is dif®cult work and violating these requirements (SFWMD 2000). Simi- many have given their best to ®nding a workable so- larly, the new South African National Water Act creates lution. The ACF story is offered here to commend these a reserve of water in each river basin containing two efforts and to illustrate that even in a complex, mul- elements: an ecological ¯ow regime and water needed tistate, politically charged negotiation with diverse in- to meet ``basic'' human needs of 26 L of water per terests, a framework for ecologically sustainable water person per day (Republic of South Africa 1998). Other management can provide a pathway for meeting both human uses are not allowed to violate these reserves. human and ecosystem needs. Experiences in both Florida and South Africa have

CONCLUSIONS shown that attaining ecological sustainability is much more feasible when ecosystem ¯ow requirements are In this paper we have sketched what we believe to assessed and protected before a river basin's water sup- be a useful roadmap for ®nding ecological sustain- plies have been extensively developed. Good examples ability in water management. We are inspired by grow- of water policy that facilitates better integration of ex- ing evidence proving that water management does not isting human needs and ecosystem requirements in need to compromise freshwater ecosystems while pro- more heavily developed watersheds are badly needed. viding for human needs. Ultimately, the goal of ecologically sustainable water Advocacy for ecological sustainability is mounting management will not be achieved until humans accept from different sectors of society as we are increasingly that there are limits to water use, and those limits are confronted with the side effects of historical water man- de®ned by what is needed by the natural systems that agement practices. Society is becoming far less tolerant support us. This implies certain burdens. Scientists and of the ®nancial expense, technological complications, conservationists must work hard to de®ne ecosystem health problems, and aesthetic degradation associated ¯ow requirements that will protect the ecological in- with water quality deterioration, invasive species in- festations, exacerbated ¯ooding, loss of species and tegrity of the affected systems. Water managers and ecosystem productivity, and other changes caused by users must be willing to live within the limits posed unsustainable water management. Whether water pol- by ecosystem ¯ow requirements even as they undergo icy leaders share an appreciation for biodiversity or further re®nement, to ef®ciently use available water not, they are forced to pursue the concept of ecologi- supplies, and commit to long-term water planning and cally sustainable water management because of the in- adaptive management. Together we must all search for herently untenable objective of satisfying society's innovative solutions, tap human creativity to address need for water in the midst of collapsing natural sys- those areas where there is con¯ict, and keep working tems. at it until we get it right. What will we need to do to move swiftly toward ACKNOWLEDGMENTS ecologically sustainable water management? We believe the answer lies in putting ecological consider- We bene®ted greatly from reviews provided by Sandra Pos- tel, Sam Pearsall, Graham Lewis, Steve Leitman, Jill Baron, ations up front along with other goals for water man- Doug Kenney, and an anonymous reviewer; and editing by agement planning, rather than treating ecological cri- Martha Hodgkins. Graphics assistance was provided by Ni- teria as compliance factors to be evaluated after a water cole Rousmaniere. Computer simulation modeling used in development plan is completed. One of the most im- this paper for the Roanoke River was performed by Brian portant lessons we learned from our involvement in the McCrodden of Hydrologics, Incorporated with Sam Pearsall of The Nature Conservancy. Modeling for the Apalachicola± ACF discussions is that speci®cation of ecosystem ¯ow Chattahoochee±Flint River basin was conducted by Steve requirements should have been given much greater at- Leitman and the Northwest Florida Water Management Dis- tention at the beginning of the negotiations, and much trict. February 2003 ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT 223

LITERATURE CITED and geomorphological concepts for instream and out-of- channel ¯ow requirements. Rivers 2:198±210. ACOE (Army Corps of Engineers). 1998. Water allocation Holling, C. S., and G. K. Meffe. 1996. Command and control for the Apalachicola±Chattahoochee±Flint River Basin and the pathology of natural resource management. Con- draft environmental impact statement, main report. Mobile servation Biology 10:328±337. district. Army Corps of Engineers, Mobile, Alabama, USA. Arthington, A. H., and M. J. Zalucki. 1998. Comparative Howitt, R. 1992. Industrialisation, impact assessment and evaluation of environmental ¯ow assessment techniques: empowerment. Indigenous Peoples and Development Is- review of methods. Occasional Paper 25/98. Land and Wa- sues, Auckland, New Zealand. ter Resources Research and Development Corporation, Huang, W., and W. K. Jones. 1997. Three-dimensional mod- Australian Capitol Territory, Canberra, Australia. eling of circulation and salinity for the low river ¯ow sea- Axelrod, L. J. 1994. Balancing personal needs with environ- son in Apalachicola Bay, FL. Water Resources Special Re- mental preservation: identifying the values that guide de- port 97-1. Northwest Florida Water Management District, cisions in ecological dilemmas. Journal of Social Issues 5: Tallahassee, Florida, USA. 85±104. IUCN (International Union for the Conservation of Nature). Baron, J. S., N. L. Poff, P. L. Angermeier, C. N. Dahm, P. H. 2000. Vision for water and nature: a world strategy for Gleick, N. G. Hairston, R. B. Jackson, C. A. Johnston, B. conservation and sustainable management of water re- D. Richter, and A. D. Steinman. 2002. Meeting ecological sources in the 21st century. International Union for the and societal needs for freshwater. Ecological Applications Conservation of Nature, Gland, Switzerland and Cam- 12:1247±1260. bridge, UK. Bingham, G. 1986. Resolving environmental disputes: a de- Iverson, R., W. Landing, B. Mortazavi, J. Fulmer, and F. G. cade of experience. Conservation Foundation, Washington, Lewis. 1997. Nutrient transport and primary productivity D.C., USA. in the Apalachicola River and Bay. Draft report to the ACF/ Bragg, O. M., and A. R. Black. 1999. Anthropogenic impacts ACT Comprehensive Study. Northwest Florida Water Man- on the hydrology of rivers and lochs. Stage 1 report: lit- agement District, Tallahassee, Florida, USA. erature review and proposed methods. University of Dun- King, J., and D. Louw. 1998. Instream ¯ow assessments for dee, Dundee, UK. regulated rivers in South Africa using the building block Carver, S., S. Frysinger, and R. Reitsma. 1996. Environ- methodology. Aquatic Ecosystem Health and Management mental modeling and collaborative decision-making: some 1:109±124. thoughts and experiences arising from the I-17 meeting. King, J. M., R. E. Tharme, and M. S. de Villiers. 2000. En- Preliminary Proceedings of the Third International Con- vironmental ¯ow assessments for rivers: manual for the ferences Workshop on Integrating Geographic Information building block methodology. Water Research Commission, Systems and Environmental Modeling, 21±25 January. Na- Pretoria, South Africa. tional Center for Geographic Information Analysis, Santa Lee, K. N. 1993. Compass and gyroscope. Island Press, Fe, New Mexico, USA. Washington, D.C., USA. Chanton, J. 1997. Examination of the coupling between pri- Lewis, F. G. 1997a. Apalachicola River and Bay water de- mary and secondary production in the Apalachicola River mand element: summary and integration of Apalachicola and Bay. Draft report to the ACF/ACT Comprehensive Bay studies. Draft report to the ACF/ACT Comprehensive Study. Northwest Florida Water Management District, Tal- Study. Northwest Florida Water Management District, Tal- lahassee, Florida, USA. lahassee, Florida, USA. Christensen, N. L. et al. 1996. The report of the Ecological Lewis, F. G., editor. 1997b. Relationships of river ¯ow and Society of America Committee on the scienti®c basis for other environmental characteristics with the structure and ecosystem management. Ecological Applications 6:665± function of biological communities in Apalachicola Bay. 691. Draft report to the ACF/ACT Comprehensive Study. North- Commission on Environmental Cooperation. 1999. Sustain- west Florida Water Management District, Tallahassee, Flor- ing and enhancing migratory bird habitat on the Upper San ida, USA. Pedro River. Final draft from the expert study team. Com- Light, H. M., M. R. Darst, and J. W. Grubbs. 1998. Aquatic munications and Public Outreach Department of the Com- habitats in relation to river ¯ow in the Apalachicola River mission on Environmental Cooperation, Montreal, Quebec, ¯oodplain, Florida. U.S. Geological Survey Professional Canada. Paper 1594. Water Resources Division, Florida District, Freeman, M. C., J. M. Nestler, and P. N. Johnson. 1997. U.S. Geological Survey, Tallahassee, Florida, USA. Riverine resources: water needs and environmental effects Maddaus, W. O. 1987. Water conservation. American Water analyses in the Alabama±Coosa±Tallapoosa and Apalach- Works Association, Denver, Colorado, USA. icola±Chattahoochee±Flint River basins. U.S. Geological Michelsen, A., and R. Young. 1993. Optioning agricultural Survey, Biological Resources Division, Patuxent Wildlife water rights for urban supplies during drought. American Research Center, Athens, Georgia, USA. Journal of Agricultural Economics 75:1010±1020. Gillilan, D. M., and T. C. Brown. 1997. Instream ¯ow pro- Natural Resources Law Center. 1996. Restoring the West's tection: seeking a balance in western water use. Island waters: opportunities for the Bureau of Reclamation. Uni- Press, Washington, D.C., USA. versity of Colorado, Boulder, Colorado, USA. Gleick, P. H. 1998. The world's water 1998±1999: the bi- Noss, R. F. 1990. Indicators for monitoring biodiversity: a ennial report on freshwater resources. Island Press, Wash- hierarchical approach. Conservation Biology 4:355±364. ington, D.C., USA. Noss, R. F., and A. Y. Cooperrider. 1994. Saving nature's Gleick, P. H. 2000. The changing water paradigm: a look at legacy: protecting and restoring biodiversity. Island Press, twenty-®rst century water resources development. Water Washington, D.C., USA. International 25:127±138. Petts, G., and P. Calow. 1996. River biota: diversity and Gunderson, L. H., C. S. Holling, and S. S. Light, editors. dynamics. Blackwell Science, London, UK. 1995. Barriers and bridges to the renewal of ecosystems Poff, N. L., J. D. Allen, M. B. Bain, J. R. Karr, K. L. Pres- and institutions. Columbia University Press, New York, tegaard, B. D. Richter, R. E. Sparks, and J. C. Stromberg. New York, USA. 1997. The natural ¯ow regime: a paradigm for river con- Hill, M. T., S. W. Platts, and R. L. Beschta. 1991. Ecological servation and restoration. BioScience 47:769±784. 224 BRIAN D. RICHTER ET AL. Ecological Applications Vol. 13, No. 1

Postel, S. 1999. Pillar of sand: can the irrigation miracle last? ers. Water law review ®nal report for policy development W. W. Norton, New York, New York, USA. for the Department of Water Affairs and Forestry, Pretoria, Postel, S., and S. Carpenter. 1997. Freshwater ecosystem ser- South Africa. vices. Pages 195±214 in G. C. Daily, editor. Nature's ser- Tharme, R. E. In press. A global perspective on environ- vices: societal dependence on natural ecosystems. Island mental ¯ow assessment: emerging trends in the develop- Press, Washington, D.C., USA. ment and application of environmental ¯ow methodologies Pringle, C. M., M. C. Freeman, and B. J. Freeman. 2000. for rivers. Rivers Research and Application. Regional effects of hydrologic alterations on riverine mac- Tharme, R. E., and J. M. King. 1998. Development of the robiota in the New World: tropical±temperate comparisons. building block methodology for instream ¯ow assessments BioScience 50:807±823. and supporting research on the effects of different mag- Railsback, S. 2001. Instream ¯ow assessment methods: guid- nitude ¯ows on riverine ecosystems. Water Research Com- ance for evaluating instream ¯ow needs in hydropower li- mission Report Number 576/1/98, Cape Town, South Af- censing. Electric Power Research Institute, Palo Alto, Cal- rica. ifornia, USA. Trush, W. J., S. M. McBain, and L. B. Leopold. 2000. At- Republic of South Africa. 1998. National Water ActÐAct tributes of an alluvial river and their relation to water policy No. 36 of 1998. Pretoria, South Africa. and management. Proceedings of the National Academy of Richter, B. D., J. V. Baumgartner, J. Powell, and D. P. Braun. Sciences 97:11858±11863. 1996. A method for assessing hydrologic alteration within Upper San Pedro River Partnership. 1998. Memorandum of ecosystems. Conservation Biology 10:1163±1174. understanding between the U.S. Bureau of Land Manage- Richter, B. D., J. V. Baumgartner, R. Wigington, and D. P. ment, U.S. Department of Defense, U.S. Forest Service, Braun. 1997b. How much water does a river need? Fresh- U.S. Geological Survey, U.S. National Park Service, Ari- water Biology 37:231±249. zona Department of Water Resources, Arizona Department Richter, B. D., D. P. Braun, M. A. Mendelson, and L. L. of Water Quality, Arizona State Land Department, Cochise Master. 1997a. Threats to imperiled freshwater fauna. Con- County, City of Sierra Vista, City of Bisbee, Town of Hu- servation Biology 11:1081±1093. achuca City, City of Tombstone, Hereford Natural Resource Richter, B. D., and H. E. Richter. 2000. Prescribing ¯ood Conservation District, and The Nature Conservancy. West- regimes to sustain riparian ecosystems along meandering ern Resource Of®ce of The Nature Conservancy, Boulder, rivers. Conservation Biology 14:1467±1478. Colorado, USA. Rogers, K., and R. Bestbier. 1997. Development of a protocol U.S. Congress. 1997. Granting the consent of Congress to for the de®nition of the desired state of riverine systems the Apalachicola±Chattahoochee±Flint River Basin Com- in South Africa. South African Wetlands Conservation Pro- pact. Public Law 105±104. U.S. Congress, Washington, gramme, Department of Environmental Affairs and Tour- D.C., USA. ism, Pretoria, South Africa. USFWS (U.S. Fish and Wildlife Service) and USEPA (U.S. Rogers, K., and H. Biggs. 1999. Integrating indicators, end- Environmental Protection Agency). 1999. Instream ¯ow points, and value systems in strategic management of the guidelines for the ACT and ACF Basins interstate water rivers of the Kruger National Park. Freshwater Biology 41: allocation formula. Report attached to letter dated October 439±451. 25, 1999, from Sam D. Hamilton, Regional Director, SFWMD (South Florida Water Management District). 2000. USFWS, and John H. Hankinson, Jr., Regional Adminis- Basis of review. South Florida Water Management District, trator, EPA, to Lindsay Thomas, Federal Commissioner, Brooksville, Florida, USA. ACT and ACF River Basins Commissions. U.S. Fish and Sparks, R. E. 1995. Need for ecosystem management of large Wildlife Service, Panama City, Florida, USA. rivers and their ¯oodplains. BioScience 45:169±182. Vickers, A. 2001. Handbook of water use and conservation. Stanford, J. A., J. V. Ward, W. J. Liss, C. A. Frissell, R. N. Waterplow Press, Amherst, Massachusetts, USA. Williams, J. A. Lichatowich, and C. C. Coutant. 1996. A Walker, K. F., F. Sheldon, and J. T. Puckridge. 1995. A per- general protocol for restoration of regulated rivers. Regu- spective on dryland river ecosystems. Regulated Rivers 11: lated Rivers 12:391±414. 85±104. Stein, B. A., L. S. Kutner, and J. S. Adams. 2000. Precious Walters, C. J., and C. S. Holling. 1990. Large-scale man- heritage: the status of biodiversity in the United States. agement experiments and learning by doing. Ecology 71: Oxford University Press, New York, New York, USA. 53±74. Swales, S., and J. H. Harris. 1995. The expert panel assess- Wigington, R. 2000. Dry year options: can the endangered ment method (EPAM): a new tool for determining envi- ®sh pay to share irrigation water in the Yampa River Basin? ronmental ¯ows in regulated rivers. Pages 125±134 in The Western Resource Of®ce of The Nature Conservancy, Boul- ecological basis for river management. John Wiley and der, Colorado, USA. Sons, Chichester, UK. WCD (World Commission on Dams). 2000. Dams and de- Tharme, R. 1996. Review of international methodologies for velopment: a new framework for decision-making. Earth- the quanti®cation of the instream ¯ow requirements of riv- scan, London, UK.