Impacts of rice production on water quality

Transcription

1 Impacts of rice production on water quality Bruce Linquist 2011 Rice Production Workshop March 21, 2011

2 Water quality and rice production The Delta is the drinking water source for over 22 million people. The Delta is also a very sensitive wetland and wildlife habitat. The Sacramento River is the single largest contributor of water to the Delta. Up to half of the water applied to a rice field drains from it and enters the Sacramento River.

3 Water quality program Since, 2003, all agriculture in California must comply with an agricultural discharge program. Irrigated Lands Regulatory Program (ILRP) The CRC implements water quality monitoring and reporting activities in compliance with the following two programs of the Central Valley Regional Water Quality Control Board (CVRWQCB): Rice Pesticides Program (RPP) monitoring and reporting. Thiobencarb Conditional Waiver for Rice (CWFR) monitoring and reporting, a rice-specific Monitoring and Reporting Program (MRP) ph, EC, DO, Temp, Turbitiy, TDS, TOC, hardness, Cu, Propanil Only commodity specific program in the ILRP Development is on-going with the regional water board for a permanent, or long term program (LT-ILRP) that includes groundwater.

4 Surface waters

5 Water quality Background In the past due to pesticide issues Currently due to pesticides and other constituents of concern Molinate

6 Management practices to improve Herbicides Control seepage Maintain hold periods to allow pesticides time to degrade water quality

7 Effect of holding times in achieving water quality goals

8 TABLE 3-5 Water Hold Requirements in Days for Thiobencarb Thiobencarb Bolero 15-G and Release Type Bolero UltraMax Single field Single field southern area only a 19 Release into tailwater recovery system or pond onto fallow field 14 b 14 b (except southern area) b Multi-growers and district release onto closed recirculating systems 6 6 Abolish 8EC Multi-growers and district release onto closed recirculating systems 6 in southern area Release into areas that discharge negligible amounts to perennial 19 6 c streams Pre-flood application: release onto tailwater recovery system Emergency release of tailwater Commissioner verifies the hydrologic isolation of the fields 6 6 NOTES: a Sacramento San Joaquin Valley defined as south of the line defined by Roads E10 and 116 in Yolo County and the American River in Sacramento County b Thiobencarb permit condition allowed Bolero 15-G label hold period of 14 days c Applies to verified hydrologically isolated fields Holding period for various pesticides TABLE 3-6 Hold Times for Insecticides, Fungicides, and Herbicides Not Covered by RPP Water Hold Time Active Ingredient Trade Name Insecticides Diflubenzuron Dimlin Insect Growth Regulator 14 days None (s)-cypermethrin Mustang 1.5 EW Insecticide 7 days None Lambda-cyhalothrin Warrior Insecticide 7 days None Methyl Parathion None 24 days None Malathion None 4 days * None Fungicides Azoxystrobin Quadris Flowable Fungicide 14 days None Herbicides Carfentrazone-ethyl Shark 5-day static 30-day release None Provisions Clomazone Cerano TM 14 days Less if closed system Cyhalofop-butyl Clincher TM 7 days None Propanil Stam TM 80 EDF 7 days None Triclopyr TEA Grandsand TM CA Herbicide 20 days Less if closed system Molinate Ordram 28 days NOTE: * Voluntary hold

9 Propanil TABLE Propanil Monitoring Results Monitoring Results (µg/l) Sampling (Reporting Limit for McCampbell Analytical <0.50 µg/l) Date CBD5 BS1 CBD1 SSB F 6/15/ ND ND ND ND 6/22/ J 2.7 ND ND 6/29/ J 2.8 ND ND 10 7/6/ ND /13/2010 ND 0.65 ND 0.97 ND 7/20/2010 ND ND 0.67 ND 1.2 7/27/2010 ND ND ND ND ND 8/3/2010 ND ND ND ND ND 2010 Results for herbicide monitoring NOTES: Concentrations are reported in µg/l (parts per billion) ND = Not detected above laboratory reporting limits J = Analyte detected below quantitation limits No numeric standard exists for propanil, so the laboratory reporting limit is used as a guideline in analyzing sampling results Thiobencarb TABLE 5-15 Summary of Detections (RPP and City Monitoring), 2010 Thiobencarb Site Detections Detections Greater than Performance Goal Range of Detected Concentrations CBD5 a 10 0 ND 1.5 µg/l BS1 a 7 0 ND 0.80 µg/l CBD1 a 9 1 ND 1.8 µg/l SSB a 5 0 ND 0.26 µg/l SR1 a 1 0 ND 0.08 µg/l SRR b 0 0 ND WSR c 0 0 ND Drain Site Totals 31 1 River Site Totals 1 0 Totals NOTES: ND = non-detect (below the method reporting limit) a RPP site b City of Sacramento intake site (as reported by the city) c City of West Sacramento intake site (as reported by the city) CBD5

10 Constituents of Concern Pesticides Physical parameters ph Dissolved oxygen Electrical conductivity Temperature Total dissolved solids Total suspended solids Nutrients Nitrogen, Phosphorus, Potassium Dissolved organic carbon (DOC) Metals Copper E. coli

11 Summary Potential issues during growing season Pesticides Potassium (?) Copper (?) DO Potential issues during the winter DOC Phosphorus Potassium (from a nutrient mgmt standpoint) No apparent problem Total dissolved solids Total suspended solids ph EC Nitrate Ammonium E. coli (drains?)

12 Why the concern over DOC DOC are known to form disinfection byproducts during drinking water treatment processes. This includes trihalomethanes

13 Why are we concerned with DOC? Sacramento River DOC USGS, Water resources investigation report,

14 What are the water quality implications resulting from the shift in straw management from burning to winter flooding?

15 Dissolved organic carbon

16 Concentration and loads Concentration only part of the story Ultimately interested in loads leaving rice fields. Loads more difficult to measure Nutrient load=concentration X water volume Net load = tail water load - water inlet load

17 Net loads (kg/ha) of carbon and nutrients leaving rice fields TOC DOC TSS TDS NH4-N NO3-N DP-P K Winter Average Inc season Burn Std dev Inc Burn Growing Average Inc season Burn Std dev Inc Burn During the winter rice fields tend to be sources for nutrients During the growing season rice fields tend to sinks for nutrients.

18 Natural Log Net Growing Season DOC Load (kg ha -1 ) 4 r 2 = p = < Effects of water 2 management on 1 DOC 0 and K loads Natural Log Total Growing Season Outflow (m 3 ha -1 ) b GCID 2 ac ft/ac Net Growing Season DOC Load (kg ha -1 ) Total Growing Season Outflow (m 3 ha -1 )

19 Subsurface water

20 Quantify N losses due to NO 3 leaching in California rice systems Background Nitrate posses a health concern in ground water Levels above 10 ppm NO 3 -N in considered a health risk by the EPA Agriculture can be a major contributor to nitrate in ground water

21 Procedure Identified 8 rice fields that included representative sites as well as extreme sites Took soil cores to a depth of 2m (7 ft) Measurements across depth of soil core Denitrification of surface soil Hydraulic conductivity of soil below root zone Glenn Colusa Colusa Yolo Yolo Sutter Butte Butte Sutter Yuba Yuba Placer Placer Sacramento Sacramento

22 Soil nitrate at different soil depths 5 Tibbitts Soil nitrate-n (ppm) Corancho Mayben Meyers Mathews Brenan Stutz McLelan Soil depth (cm)

23 Why soil nitrate levels are low in rice systems Soil nitrate levels are low in the surface soil to begin with (0.4 to 4.2 ppm) Winter weeds take up nitrate Straw immobilizes Growers do not apply NO 3 fertilizer Soils remain flooded for much of the season preventing nitrification (NH 4 to NO 3 ) Denitrification rates are very fast (NO 3 to N gas) Downward water percolation is very slow

24 Conclusion The ability to manage water is key to managing water quality Water holds for pesticides Water flows for DOC and nutrients Do not want excessive flow rates Keeping fields flooded to reduce NO3 accumulation.

25 Thank you