1. Spatial and Temporal Variations in Streamflow, Dissolved Nitrate, and Total Phosphorus in the Rio Grande from Del Norte, Colorado, to El Paso, Texas, 1993-95 By Stephanie J. Moore and Scott K. Anderholm National Water Quality Assessment Program NAWQA

2. Overview Describe spatial and temporal variations in streamflow and nutrient concentrations. Use variations in streamflow to evaluate affects of inflows and diversions? Use variations in nutrient concentrations to evaluate affects of inflows and instream processes?

3. Data Monthly water-quality samples -- collected from 1993 to 1995 Daily mean streamflow data -- calculated from continuous data

4. Rio Grande Valley Study Unit Elephant Butte And Caballo Reservoirs Rio Grande Floodway and Conveyance Channel Agricultural areas Areas of ground-water inflow

5. Spatial variations in streamflow RGDelN RGTrinch Conejos Sum1 RGLob RGTJB Chama Sum2 RGOtowi Convey RGFldwy Sum3 RGLeasb RGElP Annual mean streamflow (ft 3 /s) 0 1,200 1,000 200 800 600 400 1,400 1,600 1,800 2,000 2,200 2,400 1 2 T Sum 3 4 T Sum 5 T 7 Sum 8 9 Decreases by 650 ft 3 /s Increasing streamflow Decreasing streamflow 2 + T = Sum 1993 1994 1995

6. Daily mean streamflow (ft 3 /s) Temporal variations in streamflow 0 3,000 1,000 4,000 2,000 5,000 6,000 7,000 8,000 9,000 Otowi Taos Jxn Rio Chama

7. 1 2 T 3 4 T 5 6 T 7 8 9 0.6 0 0.2 0.8 0.4 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Dissolved nitrate (mg/L) Spatial variations in dissolved nitrate concentrations Little change above Otowi Increase between Otowi and Isleta Convey vs. Floodway Reservoir effects Increase Above El Paso

8. Temporal variations in dissolved nitrate concentrations between Otowi and Isleta Dissolved nitrate (mg/L) * RGOtowi RGIsleta 3 0 1 2 Generally, smaller nitrate concentrations during snowmelt. Smallest increases (between sites) during snowmelt. Larger concentrations during low flow. (Otowi: Dec – Feb; Isleta: Aug – Sept)

9. 3 0 1 2 RGIsleta RGConvey RGFldwy Temporal variations in dissolved nitrate concentrations between Isleta and Elephant Butte (San Marcial) Dissolved nitrate (mg/L) Isleta to Floodway at San Marcial: little change. Isleta to Convey: decrease in nitrate concentrations. Convey: largest concentrations in Aug-Sept

10. 1 2 T 3 4 T 5 6 T 7 8 9 Total phosphorus (mg/L) Spatial variations in total phosphorus concentrations 0.6 0 0.2 0.8 0.4 1.0 1.2 1.4 1.6 1.8 Little change above Otowi Convey vs. Floodway Reservoir effects Increase Above El Paso Increase between Otowi and Isleta

11. Temporal variations in total phosphorus concentrations between Otowi and Isleta Total phosphorus (mg/L) 0.5 0 1.0 * RGOtowi RGIsleta Seasonal pattern at Otowi is typical: Largest concentrations during snowmelt. Isleta: Smallest concentrations during snowmelt.

12. Temporal variations in total phosphorus concentrations between Isleta and Elephant Butte Total phosphorus (mg/L) 1.0 0 2.0 RGIsleta RGFldwy Isleta and Floodway: smallest concentrations during snowmelt. Floodway: large concentrations during monsoon and early snowmelt.

13. Spatial variations in nutrient concentrations, streamflow, and nutrient loads

14. WRIR 02-4224 http://nm.water.usgs.gov/publications.htm