Comprehensive Watershed Comprehensive Watershed Management for Central Arizona Management for Central Arizona Basins and the Valley of the Sun Basins and the Valley of the Sun
Acknowledgements • Sponsors: • Central Arizona Project • City of Peoria • In-Kind Contributors: • Arizona Department of Environmental Quality • City of Tempe • City of Scottsdale
Students Leah Bymers (M.Sc.) Shelby Flint (M.Sc.) Chris Goforth (Ph.D) Emily Hirleman (Undergrad) Nick Paretti (M.Sc.) Chad King (Ph.D, Webmaster)
http://ag.arizona.edu/limnology/watersheds
New website • ag.arizona.edu/limnology/watershed
Background • Started examining watersheds surrounding the Valley in 1996 (Lake Pleasant and the CAP Canal). • Expanded to include Roosevelt, Apache, Canyon, Saguaro, and Bartlett in 1999. • Currently assessing watershed health in all of the reservoirs surrounding the Valley including the Salt and Verde Rivers above and below them.
Rationale for a Watershed- Based Approach • What are we really trying to measure? – “environmental health”, “ecological integrity”, “biologic potential” etc. • How does this relate to drinking water quality? – Striving for “ecological integrity” inextricably brings us closer to “water quality” for municipal use.
Integrity Defined • General definition: “a systems ability to generate and maintain biotic elements through natural evolutionary processes.” (Karr 1994). • Integrity refers more to a system’s capacity and resilience than to its particular state.
Adopting integrity as a management goal does not imply maximizing any particular process rate (such as production) or compositional attribute (such as biodiversity); rather, it implies maximizing similarity to previously evolved ranges of states and process rates.
• Human impact on ecosystems typically stems from changes in physical, chemical, or biological attributes and from more than one stressor (i.e. cumulative effects and synergy). • Consequently, restoring ecological integrity must be based on a broad, holistic perspective that recognizes myriad potential constraints.
• Water quality monitoring and assessment has traditionally been compartmentalized by the requirements of specific technical disciplines and has typically been undertaken at the site scale.
• Determining what integrity is for an ecosystem means gleaning from the data anthropogenic vs. natural stressors. • Although natural systems may not be completely restorable, what often can be restored is a system’s ability to generate and maintain ecological elements through natural evolutionary processes.
Values Assessment • Management goals for watersheds (e.g., exploitation, protection, restoration) are not selected by society scientifically, but are based on prevailing values. • Scientists are rarely, if ever, charged with choosing large-scale management goals.
• The role of science in watershed management is: – To describe past, present, or future ecosystem states. – Develop prescriptions for guiding ecosystems toward societal-preferred states. – Articulate the costs and benefits of maintaining ecosystems in selected states.
The integration of physical, chemical, biological, and socioeconomic expertise needed to protect or restore an ecosystem makes watershed management a truly multidisciplinary endeavor
Specific Goals • Assessment Assessment – Determine current physical, chemical, and biological integrity of drainage basins to the Phoenix Valley. • Prediction Prediction – Based on the above data, predict each watersheds long- and short-term sustainability in light of various stressors.
Goals (cont.) • Recommendations – Based on integration of all current and potential stressors, we will make recommendations to increase or sustain ecologic integrity (e.g., “water quality”).
Sampling/Research Design • Watershed monitoring/data acquisition should account for spatial and temporal variation. • The watersheds surrounding the Valley do not start with reservoir releases, the lowest reservoirs, or treatment plant intakes.
Spatial Variability in Reservoirs
Issues of Concern (e.g., “Stressors” • Drought • Eutrophication • Rodeo-Chedeski Fire (and potential for other wildfires) • Population Growth • Perchlorate • Algal Toxins • Disinfection by-products
Drought • Despite recent precipitation events, hydrological drought persists in the southwest. • Recent precipitation may bring short-term relief. • Water year precipitation is still below average for most of the southwest.
• Since January, there have been increases in precipitation and percent of average snow water content. • However, snowpack is/was still quite low in Arizona.
• Seasonal forecasts indicate an increased probability of above average temperatures across Arizona and New Mexico throughout the spring and summer.
• There is a slightly better-than- average chance of a weak El Nino episode developing during the second half of 2004.
Long-Term Climate Forecast • Unlike El Nino/La Nina events, which usually last from 6-18 months, Pacific Decadal Oscillations (PDO) can last 20-30 years. • Positive PDO phase = colder water in the North Pacific driving the jet stream well to the North of Arizona. • Negative PDO phase = warmer water in the North Pacific enhancing the jet stream over Arizona.
Climate Summary • Possible short-term drought relief due to El Nino events. • Long-term drought may continue due to positive PDO phase.
Drought Effects on Reservoir Water Quality • Warmer than normal temperatures earlier in the spring may lead to an earlier onset of thermal stratification. • Prolonged stratification usually results in prolonged hypolimnetic anoxia.
• Earlier than normal algal blooms may exacerbate thermal stratification. • Increased strength of stratification, and subsequent hypolimnetic anoxia, may mean bioavailable nutrients released from sediments and into downstream reservoirs, rivers or canals
• Sediment nutrient release may result in increases in primary production which may lead to increased strength of stratification which means more nutrients released from sediments etc. initiating a positive feedback mechanism.
•Decreased residence time in the reservoirs, may exacerbate the possible increases in primary production.
• Water quality problems associated with drought include increases in; – Disinfection by-products – Algal toxins – Tastes and odors – Salinity/TDS/Conductivity
http://www.rangeview.arizona.edu Geospatial Tools for Natural Resource Management
Drought, Wildfire, and Water Quality; The Rodeo- Chedeski Fire and Impacts on Roosevelt and Beyond
• As stated during the last meeting, the water quality effects on the Salt River and reservoirs below it from the Rodeo-Chedeski fire will be subtle and will occur in pulses.
Chart Overlay Chart Y 30804 Mean(Flow_cfs) 121703 Mean(Turbidity_NTU) 81903 Date 52903 30603 120302 91202 0 2000 4000 6000 8000 10000 12000 14000 16000
Heavy nutrient loading following monsoon rains over burn area Y 121703 Mean(NH3-N (ppm)) 81903 Mean(NO3+NO2-N (ppm 52903 Date Mean(Total P (ppm)) 30603 Mean(TKN (ppm)) 120302 91202 0 5 10 15 20 25 30 35
But are present conditions different than post-fire conditions?
30804 121703 81903 52903 30603 120302 91202 0 500 1000 1500 2000 2500 3000 3500 4000 Mean(Flow_cfs) 50900 20800 110299 92799 82399 71999 0 500 1000 1500 2000 2500 3000 3500 4000 Mean(Flow_cfs)
Pre- and Post-Fire Nutrient Loading Y Mean(NH3-N (ppm)) Pre Pre/Post Fire Mean(NO3+NO2-N (ppm Mean(Total P (ppm)) Mean(TKN (ppm)) Post .0 .5 1.0 1.5 2.0 2.5 3.0 Y
• The detrimental effect of the pulses of suspended solids, nutrients, and other pollutants on the Salt River itself are relatively short-lived and will decrease over time. • However, the detrimental effect on Roosevelt and downstream reservoirs will probably be longer- lived.
Pre- and Post-Fire Data from Roosevelt
Chart Pre-Fire Pre/Post Fire Post-Fire 0 1 2 3 4 5 6 7 8 9 10 11 Mean(Chl a (mg/m3))
Nutrients Y SRROOC Pre-Fire Mean(Total P (mg/L)) SRROOB Site by Pre/Post Fire Mean(Nitrate+Nitrite-N (mg/L SRROOA Mean(Ammonia-N (mg/L)) SRROOC Post-Fire SRROOB SRROOA .00 .05 .10 .15 .20 Y
TOC/DOC Y SRROOC Pre-Fire Site by Pre/Post Fire SRROOB Mean(TOC (mg/L)) Mean(DOC (mg/L)) SRROOA SRROOC Post-Fire SRROOB SRROOA 0 1 2 3 4 5 6 7 8 Y
Trophic State Change Pre- and Post-Fire
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