Natural Flow Regime and Ecological Integrity of Rivers N. LeRoy Poff Department of Biology & Graduate Degree Program in Ecology Colorado State University Fort Collins, Colorado Restauración de Rios Seminario International Madrid 19.-21.9.06 In collaboration with: Diego García de Jalón (Madrid); María Alba Solans Verdu (Lleida) Restoration Science “Reference” Society Condition Degree of Degradation Current Condition Scientific Understanding - Tools - Indicators of Success Desired Future Condition Possible Goals: • clean water • uncontaminated food • aesthetic appeal • ecological - rare species / diversity - productive fishery Political context Action From the European Union Water Framework Directive (WFD), under “Surface water: Ecological Protection” (http://www.europa.eu.int/comm/environment/water/waterframework/overview.html): “As no absolute standards for biological quality can be set which apply across the Community, because of ecological variability, the controls are specified as allowing only a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact.” From the European Union Water Framework Directive (WFD), under “Surface water: Ecological Protection” (http://www.europa.eu.int/comm/environment/water/waterframework/overview.html): “As no absolute standards for biological quality can be set which apply across the Community, because of ecological variability, the controls are specified as allowing only a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact.” From the European Union Water Framework Directive (WFD), under “Surface water: Ecological Protection” (http://www.europa.eu.int/comm/environment/water/waterframework/overview.html): “As no absolute standards for biological quality can be set which apply across the Community, because of ecological variability, the controls are specified as allowing only a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact.” “ … ecological protection should apply to all waters: the central requirement of the Treaty is that the environment be protected to a high level in its entirety.” From the European Union Water Framework Directive (WFD), under “Surface water: Ecological Protection” (http://www.europa.eu.int/comm/environment/water/waterframework/overview.html): “As no absolute standards for biological quality can be set which apply across the Community, because of ecological variability, the controls are specified as allowing only a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact.” “ … ecological protection should apply to all waters: the central requirement of the Treaty is that the environment be protected to a high level in its entirety.” What is the entirety? … a self-sustaining ecosystem with natural biodiversity and with the ability to respond dynamically to future changes … … restore fluvial processes Ecological Processes Ecosystem Function (production) Short-term Goods & Services Biotic Assemblage (biodiversity) Adaptive Capacity and Long-term Sustainability What does science tell us about how rivers “function”? Fundamental, general principle: River ecosystems are naturally dynamic and “disturbance driven.” River discharge (flow) is the prime generator of natural variability and disturbance: Floods and droughts are natural disturbances that directly kill organisms and indirectly affect the amount and quality of habitat for aquatic and riparian species. Flow is the “maestro” that orchestrates much of the complexity and heterogeneity at the core of river ecosystems. NOTE: Other factors also important (e.g., water quality) Key role of Flow Regime Poff et al. 1997. BioScience Structure and function of river ecosystem, and the adaptations of its constituent species, are dictated by the pattern of temporal variation in river flows. Rivers differ in their natural flow regimes. Key components of hydrologic variation: magnitude - frequency - duration - timing - rate-of-change - Variation over many time scales How does flow regime regulate ecological processes? Bunn & Arthington. 2002. Environmental Management Just like every region has a climate, each river has a natural flow regime, but rivers within the same region may have different flow regimes due to other factors that regulate rain-runoff processes: •geology, soils, •vegetative cover •river size Rivers vary in flow regimes in terms of … magnitude, frequency, duration, timing, rate-of-change At the scale of regions or countries, there is “diversity” in flow regimes. 2 Distinctly Different Natural Flow Regimes > 1 flood per year Frequent dry periods No seasonal timing 1 flood per year No dry periods High seasonal timing Natural Flow Regimes in the U.S. Poff & Ward (1990), Poff (1996). Examples showing how aquatic and riparian species react to natural flow regimes Federally threatened floodplain wetland plant requires flooding to suppress competitors and persist Boltonia decurrens restricted to open, wetland habitats in the Illinois River floodplain. Species produces many seeds Populations declining Flooding required for plant’s success - creates open, moist habitats with lots of sunlight Experiments show that without flooding, competitor species shade out native plant. Cottonwood (Populus) gallery forests (western N.A.) Require floodplain inundation at right time of year for right amount of time Flood timing regulates … production of fish (salmon) in California mediterranean stream. Natural winter floods: - species of predator-resistant insect herbivore declines - energy goes to herbivores that can be eaten by fish Loss of winter floods (dams): - “armored” insect species thrives - energy cannot be transferred to fish predatorresistant herbivore (after Wootton et al. 1996, Science) (after Power et al 1990) Natural Flow Regimes in Spain Example of 7 Rivers in Spain Narcea Aragón Sorbe (Tajo) Jarama (Tajo) Cabriel Guadalquivir Grande R Sorbe Muriel (71-79) R. Sorbe Muriel (71-79) 3 3 2,5 2,5 Qmonth/Qannual 2 2 1,5 1,5 1 1 0,5 0,5 CV 0 0 OCT NOV DES JAN FEB MAR APR MAI JUN R. Jarama Algete (40-71) Sorbe (Tajo) R. Jarama Algete (40-71) 3 2,5 Qmonth/ Qannual 2 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP JUL AUG SEP JUN JUL 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0 CV OCT NOV DEC JAN FEB MAR APR MAI JUN AUG SEP JUL AUG SEP R. Guadalquivir Sta. Maria (43-88) R. Guadalquivir Sta. Maria (43-88) 3,0 2 1,8 2,5 1,6 Qmonth/Qannual 2,0 CV 1,4 1,2 1 1,5 0,8 1,0 0,6 0,4 0,5 0,2 0 0,0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP Guadalquivir Jarama (Tajo) R Sorbe Muriel (71-79) R. Sorbe Muriel (71-79) 3 3 2,5 2,5 Qmonth/Qannual 2 2 1,5 1,5 1 1 CV Sorbe (Tajo) 0,5 0,5 0 0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP AUG SEP Jarama (Tajo) R. Jarama Algete (40-71) R. Jarama Algete (40-71) 3 2,5 Qmonth/ Qannual 2 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0 CV OCT NOV DEC JAN AUG SEP FEB MAR APR MAI JUN JUL AUG SEP Cabriel R. Cabriel 112 (56-72) R. Cabriel 112 (56-72) R. Guadalquivir Sta. Maria (43-88) R. Guadalquivir Sta. Maria (43-88) 3,0 2 3,0 1,8 2,5 2 1,6 Qmonth/Qannual 2,0 1,8 CV 1,4 2,5 1,2 Qmonth/ Qannual 1 1,5 0,8 1,0 0,6 1,4 1,5 1,2 1 0,4 0,5 0,2 0 0,0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP CV 0,8 1,0 Guadalquivir 1,6 2,0 0,6 0,4 0,5 Grande 0,2 0 0,0 OCT NOV DES JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DES JAN FEB MAR APR MAY JUN JUL AUG SEP R. Grande Coin (80-99) R. Grande Coin (80-99) 2 2,5 1,8 1,6 2 Qmonth/ Qannual CV 1,4 1,5 1,2 1 0,8 1 0,6 0,5 0,4 0,2 0 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP R. Narcea Cangas (66-81) R. Narcea Cangas (66-81) 2 3 1,8 2,5 1,6 Qmonth/ Qannual 1,4 2 CV 1,2 1 1,5 0,8 1 Narcea 0,6 0,4 0,5 0,2 0 0 OCT NOV DEC JAN FEB MAR APR MAI JUN OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP JUL AUG SEP Aragón R. Aragon Yesa (14-60) R. Aragon Yesa (14-60) 3 2 1,8 1,6 1,4 1,2 Qmonth/ Qannual 2,5 2 1,5 1 R Sorbe Muriel (71-79) R. Sorbe Muriel (71-79) 3 3 2,5 0,5 2,5 Qmonth/Qannual 2 2 1,5 1,5 1 1 0,5 0,5 0 0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL CV 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP AUG SEP CV 1 0,8 0,6 0,4 0,2 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP Sorbe (Tajo) Jarama (Tajo) R. Jarama Algete (40-71) R. Jarama Algete (40-71) 3 2,5 Qmonth/ Qannual 2 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL 2 1,8 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0 CV OCT NOV DEC JAN AUG SEP FEB MAR APR MAI JUN JUL AUG SEP Cabriel R. Guadalquivir Sta. Maria (43-88) R. Guadalquivir Sta. Maria (43-88) R. Cabriel 112 (56-72) R. Cabriel 112 (56-72) 3,0 2 1,8 2,5 3,0 2 1,6 Qmonth/Qannual 2,0 1,8 2,5 CV 1,4 1,6 Qm onth/ Qannual 2,0 1,4 0,8 1,5 1,2 1 0,6 1,0 1,2 1 1,5 1,0 0,6 0,2 0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP 0,4 0,5 0,2 0,0 CV 0,8 0,4 0,5 0,0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP Guadalquivir 0 OCT NOV DES JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DES Grande R. Grande Coin (80-99) R. Grande Coin (80-99) 2 2,5 1,8 1,6 2 Qmonth/ Qannual CV 1,4 1,5 1,2 1 0,8 1 0,6 0,5 0,4 0,2 0 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP JAN FEB MAR APR MAY JUN JUL AUG SEP What happens when natural flow regimes are altered? Sources of flow alteration - Land Use Change - Agricultural conversion - Urbanization - Water Schemes - Diversions - Groundwater pumping - Dams Consequences of Flow Alteration? Local Effects: - downstream habitat - downstream temperature - biotic interactions - floodplain isolation, etc. Landscape Effects: - fragmentation of networks - regional homogenization - land-ocean processes Ecological Processes Ecosystem Function (production) Short-term Goods & Services Biotic Assemblage (biodiversity) Adaptive Capacity and Long-term Sustainability Recent Literature Review of Ecological Responses to Flow Alteration (NL Poff and D. Pepin, unpublished) • >100 published papers (and growing) • Characterized by: – Type of flow alteration – Ecological response • Diversity/Ecosystem function • Flora/fauna • Channel/floodplain – Geographic distribution M ac ro in ga M ac r an ib s ns rd ia Bi s s ph h p o e yt Am ri or pa e Ri te es ra sh eb Fi rt 0 Al ve Number of Studies Ecological Responses 40 35 30 25 20 15 10 5 Magnitude of Flow 55% Within-channel responses: •Life cycle disruption Number of Studies 28 •Loss of sensitive species 24 •Reduced diversity 20 •Wash-out and/or stranding 16 •Reduced densities of aquatic organisms 12 •Altered energy flow 8 •Invasion or establishment of exotics 4 0 Increased variation Flow stabilization Magnitude of Flow Riparian responses: 55% • Invasion/establishment of exotics Number of Studies 14 • Reduction /elimination of recruitment 12 10 • Encroachment of vegetation into channels 8 6 4 2 0 Increased variation Flow stabilization 16% Timing of Flow Number of Studies 12 •Disrupt life cycle cues 10 • Reduced aquatic and riparian community diversity 8 • Invasion/establishment of exotics 6 4 2 0 Shift in Seasonality of peak Decreased predictability Increased predictability Literature Review Reveals • Further confirmation that flow alteration has dramatic ecological effects – Reduced species diversity in response to many altered flow components – Shift in community dominants – Establishment of non-native species – Effects on ecosystem function not well-studied • Flow alteration alone is important Reviews of Ecological Responses to Flow Regime Alteration Poff et al. 1997. BioScience Bunn & Arthington. 2002. Environmental Management Lytle & Poff 2004. Trends in Ecology & Evolution. Spanish Dams and Flow Regimes Narcea Arroyo Aragón Najerilla Sorbe (Tajo) Jarama (Tajo) Cabriel Júcar Guadalquivir Grande Effects of Dams • Daily hydrograph • Monthly hydrograph Arroyo (Ebro) 1917-1944 Arroyo (Ebro) 1917-1944 2 30 1,8 1,6 1,4 20 1,2 CV Q (m3/s) Before 25 15 1 0,8 10 0,6 0,4 5 0,2 0 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Arroyo (Ebro) 1945-2001 Arroyo (Ebro) 1945-2001 30 2 25 1,8 1,6 1,4 1,2 15 CV Q (m3/s) After 20 1 0,8 10 0,6 0,4 5 0,2 0 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Winter floods Summer low flows Summer floods Winter floods Summer low flows Summer floods -Spanish Dams reverse normal seasonal signals of high flows and low flows “homogenize” regional differences in natural flow regimes R. Narcea Cangas (66-81) 3 2,5 Narcea Qmonth/ Qannual 2 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP Aragón R. Aragon Yesa (14-60) 3 Qmonth/ Qannual 2,5 2 1,5 R. Sorbe Muriel (71-79) 1 3 0,5 2,5 0 Qmonth/Qannual OCT NOV DEC JAN FEB MAR APR MAI JUN 2 JUL AUG SEP 1,5 1 0,5 0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG SEP Sorbe (Tajo) Jarama (Tajo) R. Jarama Algete (40-71) 3 2,5 Qmonth/ Qannual 2 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP Cabriel R. Cabriel 112 (56-72) R. Guadalquivir Sta. Maria (43-88) 3,0 3,0 2,5 2,5 Qmonth/ Qannual 2,0 Qmonth/Qannual 2,0 1,5 1,5 1,0 1,0 0,5 0,5 0,0 0,0 OCT NOV DES JAN FEB MAR APR MAI JUN JUL AUG OCT NOV DES SEP Guadalquivir Grande R. Grande Coin (80-99) 2,5 2 Qmonth/ Qannual 1,5 1 0,5 0 OCT NOV DEC JAN FEB MAR APR MAI JUN JUL AUG SEP JAN FEB MAR APR MAY JUN JUL AUG SEP Options for restoration? •Dam removal Recent history in U.S. - mostly small •Manage dams to restore components of natural flow regime through “adaptive management” (Stanford et al. 1996, Poff et al. 2003) Natural Regulated Re-regulated Next Steps? Characterize Natural Flow Regime Determine Degree of Hydrologic Alteration Restoration Science Society Condition Degree of Degradation Current Condition ??? Prescribe Flow Regime for Restoration; Monitor Ecological Responses “Reference” Scientific Understanding - Tools - Indicators of Success Desired Future Condition Possible Goals: • clean water • uncontaminated food • aesthetic appeal • ecological - rare species / diversity - productive fishery Political context Action Conduct National Survey to determine “types” of natural flow regimes across Spain. Use “types” to assist goal planning for restoration planning on national scale. Thank you for your attention Special thanks to: Marta González del Tánago; Ministerio de Medio Ambienta