Impacts of rice production on water quality

Bruce Linquist2011 Rice Production Workshop

March 21, 2011

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.

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.

Surface waters

Water quality

• Background– In the past due to pesticide issues– Currently due to pesticides and other

constituents of concern Molinate

Management practices to improve water quality

• Herbicides– Control seepage– Maintain hold

periods to allow pesticides time to degrade

Effect of holding times in achieving water quality goals

Holding period for various

pesticides

TABLE 3-5Water Hold Requirements in Days for Thiobencarb

Release Type

ThiobencarbBolero® 15-G and Bolero® UltraMax

Abolish™8EC

Single field 30 19Single field southern area onlya 19 —Release into tailwater recovery system or pond onto fallow field (except southern area)b

14b 14b

Multi-growers and district release onto closed recirculating systems 6 6Multi-growers and district release onto closed recirculating systems in southern area

6 —

Release into areas that discharge negligible amounts to perennial streams

19 6c

Pre-flood application: release onto tailwater recovery system — —Emergency release of tailwater 19 19Commissioner verifies the hydrologic isolation of the fields 6 6NOTES: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 Countyb Thiobencarb permit condition allowed Bolero® 15-G label hold period of 14 daysc Applies to verified hydrologically isolated fields

TABLE 3-6Hold Times for Insecticides, Fungicides, and Herbicides Not Covered by RPP

Active Ingredient Trade NameWater Hold

Time ProvisionsInsecticides

Diflubenzuron Dimlin® Insect Growth Regulator 14 days None(s)-cypermethrin Mustang® 1.5 EW Insecticide 7 days NoneLambda-cyhalothrin Warrior® Insecticide 7 days NoneMethyl Parathion None 24 days NoneMalathion None 4 days* None

FungicidesAzoxystrobin Quadris® Flowable Fungicide 14 days None

HerbicidesCarfentrazone-ethyl Shark® 5-day static

30-day releaseNone

Clomazone CeranoTM 14 days Less if closed systemCyhalofop-butyl ClincherTM 7 days NonePropanil StamTM 80 EDF 7 days NoneTriclopyr TEA GrandsandTM CA Herbicide 20 days Less if closed systemMolinate Ordram® 28 days

NOTE:* Voluntary hold

2010 Results for herbicide

monitoring

TABLE 5-122010 Propanil Monitoring Results

Sampling Date

Monitoring Results (µg/L)(Reporting Limit for McCampbell Analytical <0.50 µg/L)

CBD5 BS1 CBD1 SSB F6/15/2010 3.8 ND ND ND ND6/22/2010 5.0 0.65J 2.7 ND ND6/29/2010 2.2J 2.8 ND ND 107/6/2010 1.7 4.4 2.0 ND 0.657/13/2010 ND 0.65 ND 0.97 ND7/20/2010 ND ND 0.67 ND 1.27/27/2010 ND ND ND ND ND8/3/2010 ND ND ND ND ND

NOTES:Concentrations are reported in µg/L (parts per billion)ND = Not detected above laboratory reporting limitsJ = Analyte detected below quantitation limitsNo numeric standard exists for propanil, so the laboratory reporting limit is used as a guideline in analyzing sampling results

TABLE 5-15Summary of Detections (RPP and City Monitoring), 2010

Site

Thiobencarb

DetectionsDetections Greater than

Performance GoalRange of Detected

ConcentrationsCBD5a 10 0 ND – 1.5 µg/LBS1a 7 0 ND – 0.80 µg/L

CBD1a 9 1 ND – 1.8 µg/LSSBa 5 0 ND – 0.26 µg/LSR1a 1 0 ND – 0.08 µg/LSRRb 0 0 NDWSRc 0 0 ND

Drain Site Totals 31 1

River Site Totals 1 0

Totals 32 1 -NOTES:ND = non-detect (below the method reporting limit)aRPP site bCity of Sacramento intake site (as reported by the city)cCity of West Sacramento intake site (as reported by the city)

CBD5

Propanil

Thiobencarb

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

SummaryNo apparent problem

– Total dissolved solids– Total suspended solids– pH– EC– Nitrate– Ammonium– E. coli (drains?)

Potential issues during growing season– Pesticides– Potassium (?)– Copper (?)– DO

Potential issues during the winter

– DOC– Phosphorus– Potassium (from a nutrient

mgmt standpoint)

Why the concern over DOC

• DOC are known to form disinfection by-products during drinking water treatment processes.– This includes

trihalomethanes

Sacramento River DOC

USGS, 2003. Water resources investigation report, 03-4070.

Why are we concerned with DOC?

What are the water quality implications resulting from the

shift in straw management from burning to winter flooding?

Dissolved organic carbon

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

Net loads (kg/ha) of carbon and nutrients leaving rice fields

TOC DOC TSS TDS NH4-N NO3-N DP-P KWinter Average Inc 39.1 31.6 83 107 0.2 -0.1 0.3 5.8

season Burn 18.8 15.0 124 152 0.5 0.1 1.4 14.8

Std dev Inc 64.8 55.8 104 122 0.3 0.4 0.7 9.3

Burn 43.2 34.1 302 323 1.2 0.1 3.7 37.3

Growing Average Inc -4.2 -2.7 -39.9 -245.8 0.2 -0.3 -0.2 -4.0

season Burn 1.4 -0.4 -36.3 -397.3 -0.1 0.4 -0.1 -3.5

Std dev Inc 9.0 7.0 175.2 376.9 0.5 0.4 0.3 3.8

Burn 14.8 12.3 134.6 275.0 0.2 2.1 0.5 3.0

During the winter rice fields tend to be sources for nutrientsDuring the growing season rice fields tend to sinks for nutrients.

Total Growing Season Outflow (m3 ha-1)

0 2000 4000 6000 8000 10000 12000 14000 16000

Net

Gro

win

g S

easo

nD

OC

Loa

d(k

g ha

-1)

-20

-10

0

10

20

30

40

50

Natural LogTotal Growing Season Outflow (m3 ha-1)

6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0

Nat

ural

Log

Net

Gro

win

g S

easo

nD

OC

Loa

d(k

g ha

-1)

0

1

2

3

4

b

r2 = 0.8603p = < 0.0001

Effects of water management on DOC and K loads

2 ac ft/ac

GCID

Subsurface water

Quantify N losses due to NO3leaching in California rice systems

• Background– Nitrate posses a health concern in ground

water• Levels above 10 ppm NO3-N in considered a

health risk by the EPA– Agriculture can be a major contributor to

nitrate in ground water

Glenn

Colusa

Butte

Yolo

Yuba

Sacramento

Placer

Sutter

GlennButte

Yolo

Colusa

Sacramento

SutterYuba

Placer

• 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

Procedure

Soil nitrate at different soil depths

0

1

2

3

4

5

0 50 100 150 200

Soil

nitr

ate-

N (p

pm)

Soil depth (cm)

Tibbitts

Corancho

Mayben

Meyers

Mathews

Brenan

Stutz

McLelan

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 NO3 fertilizer• Soils remain flooded for much of the season

preventing nitrification (NH4 to NO3)• Denitrification rates are very fast (NO3 to N gas)• Downward water percolation is very slow

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.

Thank you