Presentation on theme: "Salt and Selenium in Grand Valley Rivers and Streams Joshua Linard U.S. Geological Survey Hydrologist"— Presentation transcript:
Salt and Selenium in Grand Valley Rivers and Streams Joshua Linard U.S. Geological Survey Hydrologist firstname.lastname@example.org
Presentation Outline Importance of salt and selenium Environmental processes controlling the movement of salt and selenium Water-quality standards for salt and selenium Salt and selenium in the Colorado River Salt and selenium in Grand Valley tributaries Concentration vs. load Control initiatives Current investigations
What are Salt and Selenium? Salt – Total Dissolved Solids: the mass of all cations and anions in an aqueous solution Selenium – A naturally occurring trace element It’s essential to life, but in excess can be harmful
Why Study Salt and Selenium? High salinity water – Clogs and corrodes household pipes and fixtures – Limits agricultural productivity High selenium in water – Limits reproductive ability and can even be fatal to biological organisms – Colorado Pike Minnow, Razor Back Sucker, Boney Tail Chub, Hump Back Chub
Concentration vs Load Seasonality in salt and selenium are, generally, explored in units of … – Concentration Units of mass/volume – Load Units of mass/time – Salinity: tons/day – Selenium: lbs/day
Water-Quality Standards Standards focus on concentrations Colorado Department of Health and Environment – Salinity Established in 1976 for the entire Colorado River Basin Flow-weighted annual values shouldn’t exceed 723 mg/l (ppm) below Hoover Dam – Selenium The water-quality standards are the 85 th percentile for the most recent 5 year period – If 100 samples are available, 85 must be below the standard Established in 2000 Acute = 18.4 μg/l (ppb) Chronic = 4.6 μg/l (ppb)
Water-Quality Standards for Salinity and the Grand Valley Salinity standard at Hoover Dam: 723 mg/L Stream GageMean-Daily Salinity Concentration (mg/L) Colorado River near Cameo, CO368 Gunnison River near Grand Junction, CO786 Colorado River near Colorado-Utah State Line604 Persigo Wash at River Road2,063
Water-Quality Standards for Selenium and the Grand Valley CDPHE chronic standard for selenium: 4.6 μg/L Stream GageMean-Daily Selenium Concentration (μg/L) Colorado River near Cameo, CO0.6 Gunnison River near Grand Junction, CO4.5 Colorado River near Colorado-Utah State Line4.0 Persigo Wash at River Road35.5
Why are concentrations so much higher in tributaries than in the Colorado River? Seasonal changes in the availability of water effect the amount of salt and selenium in streams – The Colorado River has more water to dilute tributary inputs of salt and selenium – Tributary water has more interaction with the Mancos Shale in the Grand Valley Leib, K.J. 2008. Concentrations and Loads of Selenium in Selected Tributaries to the Colorado River in the Grand Valley, Western Colorado, 2004-2006. U.S. Geological Survey Scientific Investigations Report 2008-5036.
Concentration and Load vs Streamflow Relationships to streamflow are general At a particular point, as flow increases the load increases and concentration decreases Vary between salt and selenium Vary from place to place
Concentrations and Loads of Salt and Selenium Measured at the Colorado River near Colorado- Utah State Line
Concentrations and Loads of Salt and Selenium Measured at Persigo Wash at River Road
Salt and Selenium Control Management options – Increase flow to dilute salt and selenium Not really an option in the arid environment – Decrease load to lower concentrations Control initiatives are aimed at minimizing loads – Minimize source loads – Decreases tributary loads – Decreases concentrations in the Colorado River
Methods to Control Salt and Selenium Irrigation delivery system improvements – Lining and piping of canals and laterals Irrigation system improvements – Sprinklers, drips, micro, etc. Best Management Practices for residential areas Line Ponds Indirect effects from land-use change and population growth
Effects of Land-use Change on Source Loads 1.Quantify irrigation water use and deep percolation in representative areas where agricultural land has been converted to suburban use. 2.Compare irrigation water use and deep percolation at similar agricultural and suburban sites in the Grand Valley. 3.Quantify deep percolation from pond seepage for a selected number of ponds. From Mayo, J.W. 2008. Estimating the effects of conversion of agricultural land to urban land on deep percolation of irrigation water in the Grand Valley, Western Colorado. U.S. Geological Survey Scientific Investigations Report 2008-5086.
22 Grand Valley Sites Ponds Weather Stations Homes & Fields Explanation 14 Homes 4 Gated-Pipe Fields 3 Ponds 2 CSU Weather Stations Monitored for 2 irrigation seasons (2005 & 2006)
26 Irrigation Water Use and Deep Percolation (average acre-feet of water per acre for irrigation season) 1 Acreage for ¼ acre subdivisions in study was 40 percent irrigated on average 2 Acreage for 5 acre estates in study was 32 percent irrigated on average 3 Acreage for gated-pipe and alfalfa sites was assumed to be 90 percent irrigated 4 Acreage for irrigation holding ponds was assumed to be 100 percent covered with water 5 Numbers in parentheses are the range of values Subdivision Lots (bluegrass) 1 n=10 5 Acre Estates (bluegrass) 2 n=7 5 Acre Estates (native, orchard grass) 2 n=3 Gated Pipe Fields (orchard grass) 3 n=4 NRCS Alfalfa Sites 3 n=67 Irrigation Holding Ponds 4 n=4 Irrigation Water Use (ac-ft/ac) 1.1 (0.8 – 1.2) 5 0.9 (0.8 – 1.3) 0.3 (0.1 – 0.9) 1.5 (0.6 – 2.7) 3.8 (1.6 – 5.8) n/a Deep Percolation (ac-ft/ac) 0.14 (0.00 – 0.42) 0.08 (0.01 – 0.17) 0.0 (0.0 – 0.04) 0.6 (0.0 – 1.5) 1.27 (0.0 – 3.3) 9.55 (8.2 – 11.8)
27 Salt Loading (tons per acre per year) NRCS salt-loading factor for the Grand Valley is 4.1 tons per acre-foot of water applied, with an estimated 50 percent of the load reaching the Colorado River. Subdivision Lots (bluegrass) n=10 5 Acre Estates (bluegrass) n=7 5 Acre Estates (native, orchard grass) n=3 Gated Pipe Fields (orchard grass) n=4 NRCS Alfalfa Sites n=67 Irrigation Holding Ponds n=4 0.280.170.01.372.8919.6
Can we see the effects of their implementation in the water-quality of the streams? Stream Gage1986-2003 Colorado River near Cameo, CO-193,000 Gunnison River near Grand Junction, CO-202,000 Colorado River near Colorado-Utah State Line-322,000 From 1986 to 2003 the salinity load measured at the Colorado-Utah Stateline has decreased by over 300,000 tons. Butler, D.L., 1996, Trend analysis of selected water-quality data associated with salinity-control projects in the Grand Valley, in the Lower Gunnison River Basin, and at Meeker Dome, Western Colorado: U.S. Geological Survey Water-Resources Investigations Report 95-4274, 38 p. Bauch, N.J., and Spahr, N.E., 1998, Salinity Trends in Surface Waters of the Upper Colorado River Basin, Colorado: Journal of Environmental Quality, v. 27, no. 3, p. 640- 655.Journal of Environmental Quality Leib, K.J. and Bauch, N.J., 2007, Salinity trends in the Upper Colorado River Basin upstream from the Grand Valley Salinity Control Unit, Colorado, 1986-2003, U.S. Geological Survey Scientific Investigations Report 2007-5288.
Summary Underlying geology is the source of salt and selenium – Ground water transports salt and selenium to the rivers and streams in the Grand Valley Water-quality at the Colorado-Utah State Line meets standards Concentrations and Loads vary – Seasonally – Between salt and selenium – Place to place
Summary Minimizing source loads in tributaries of the Grand Valley, minimizes concentrations in the Colorado River Controlling sources of salt and selenium – Irrigation practices – Best management practices – Land-use Conversion from previously irrigated land to residential reduces source loading Long-term trends indicate control initiatives are working