Water Issues & Agrichemicals Often linked Water issues also include sedimentation, turbidity, O 2...

Water Issues & Agrichemicals

• Often linked

• Water issues also include sedimentation, turbidity, O2 levels, etc.

• Impacts– Local– Landscape– Regional– ?


• Animal feedlots

• Irrigation

• Cultivation

• Pastures

• Dairy Farming

• Orchards

• Aquaculture

How?


Leading sources of water quality impairment in the United States (US-EPA, 1994)

Rank Rivers Lakes Estuaries

1 Agriculture Agriculture Municipal point sources

2 Municipal point sources Urban runoff/storm sewers Urban runoff/storm sewers

3 Urban runoff/storm Hydrologic/habitat modification Agriculture

4 Resource extraction Municipal point sources Industrial point sources

5 Industrial point sources On-site wastewater Resource extraction

Similar findings in Europe and other areas


Percent of assessed river length and lake area impacted (US-EPA, 1994)

Source of pollution Rivers (%) Lakes (%) Nature of pollutant Rivers (%) Lakes(%)

Agriculture 72 56 Siltation (sediment) 45 22

Municipal point sources 15 21 Nutrients 37 40

Urban runoff/storm sewers 11 24 Pathogens 27

Resource extraction 11 Pesticides 26

Industrial point sources 7 Organic enrichment DO 24 24

Silviculture 7 Metals 19 47

Hydrologic/habitat modification 7 23 Priority organic 20

On-site wastewater disposal 16 chemicals

Flow modification 13


Number of States reporting groundwater contamination(maximum possible is 50) (US-EPA, 1994)

Pollutants No. of States Pollutants No. of States

Nitrates 49 Volatile organic substances 48

Petroleum products 46 Metals 45

Pesticides 43 Brine/salinity 37

Synthetic organic substances

36 Arsenic 28

Other substances 26 Other agricultural chemicals 23

Radioactive material 23 Fluoride 20

Other inorganic substances 15

Agricultural impacts on water quality Agricultural

activity Impacts

Surface water Groundwater

Tillage/ploughing Sediment/turbidity: sediments carry phosphorus and pesticides adsorbed to sediment particles; siltation of river beds and loss of habitat, spawning ground, etc.

Fertilizing Runoff of nutrients, especially phosphorus, leading to eutrophication causing taste and odour in public water supply, excess algae growth leading to deoxygenation of water and fish kills.

Leaching of nitrate to groundwater; excessive levels are a threat to public health.

Manure spreading Carried out as a fertilizer activity; spreading on frozen ground results in high levels of contamination of receiving waters by pathogens, metals, phosphorus and nitrogen leading to eutrophication and potential contamination.

Contamination of ground-water, especially by nitrogen

Pesticides Runoff of pesticides leads to contamination of surface water and biota; dysfunction of ecological system in surface waters by loss of top predators due to growth inhibition and reproductive failure; public health impacts from eating contaminated fish. Pesticides are carried as dust by wind over very long distances and contaminate aquatic systems 1000s of miles away (e.g. tropical/subtropical pesticides found in Arctic mammals).

Some pesticides may leach into groundwater causing human health problems from contaminated wells.

Feedlots/animal corrals

Contamination of surface water with many pathogens (bacteria, viruses, etc.) leading to chronic public health problems. Also contamination by metals contained in urine and faeces.

Potential leaching of nitrogen, metals, etc. to groundwater.

Irrigation Runoff of salts leading to salinization of surface waters; runoff of fertilizers and pesticides to surface waters with ecological damage, bioaccumulation in edible fish species, etc. High levels of trace elements such as selenium can occur with serious ecological damage and potential human health impacts.

Enrichment of groundwater with salts, nutrients (especially nitrate).

Clear cutting Erosion of land, leading to high levels of turbidity in rivers, siltation of bottom habitat, etc. Disruption and change of hydrologic regime, often with loss of perennial streams; causes public health problems due to loss of potable water.

Disruption of hydrologic regime, often with increased surface runoff and decreased groundwater recharge; affects surface water by decreasing flow in dry periods and concentrating nutrients and contaminants in surface water.

Silviculture Broad range of effects: pesticide runoff and contamination of surface water and fish; erosion and sedimentation problems.

Aquaculture Release of pesticides (e.g. TBT1) and high levels of nutrients to surface water and groundwater through feed and faeces, leading to serious eutrophication.

1 TBT .= Tributyltin


• Sedimentation and erosion


Selected values for sediment loss

Location Land use Soil loss (t/ha/yr)

Italy Wheat Maize Pasture

5.614 18.767 2.224

Philippines Reforested and agricultural

22-39.7

Morocco Arid, grazing 25.0-59.0

Kenya Semi-arid grazing 79.5

Bolivia Andean arid, semi-arid

5.21-51.8

United Kingdom

Agriculture 1.9 (net)

Lesotho Agriculture 7.8 (net)


Increases in sediment yield caused by land use change(Walling and Webb, 1983; Ostry, 1982)

Land use change Increase in sediment yield

Rajasthan, India Overgrazing × 4-18

Utah, USA Overgrazing of rangeland × 10-100

Oklahoma, USA Overgrazing and cultivation × 50-100

Cultivation × 5-32

Texas, USA Forest clearance and cultivation × 340

N. California, USA Conversion of steep forest to grassland

× 5-25

Mississippi, USA Forest clearance and cultivation × 10-100

S, Brazil Forest clearance and cultivation × 4500

Westland, N. Zealand Clearfelling × 8

Oregon, USA Clearfelling forest × 39

Ontario, Canada Conversion to agriculture × 14


"Eutrophication" is the enrichment of surface waters with plant nutrients. While eutrophication occurs naturally, it is normally associated with anthropogenic sources of nutrients.

Agriculture is a major factor in eutrophication of surface waters.


Selected values for nutrient losses

Location Land use Phosphorus (kg/ha/yr) Nitrogen (kg/ha/yr)

Southern Ontario Cropland 0.415

Unimproved 0.08

Maize, potatoes 26.0

Cereals, beans. veg. & tobacco 3.6

Hay, unimproved pasture 0.1

Unimproved 0.0

Great Lakes Basin (N. America) Cropland 0.2-37.1

Hungary Cropland 1.142

Denmark & Netherlands Livestock/crop systems 316

USA Cropland 64

Côte d'Ivoire Agriculture 29.0 98


Relative leaching losses of nitrogen and phosphorus (% change between no fertilizer and with fertilizer)

Management Crop Percent change

P N

Rotation Maize +10 +65

Oats, alfalfa - 05 +33

Alfalfa 1st year +17 - 08

Alfalfa 2nd yr +59 +09

Continuous Maize +12 +102

Bluegrass sod +12 - 69

Average +17 +27


• Water redistribution

http://www.usda.gov/oc/photo/85c0114.jpg


ProductWater Requirement by area

(liters/m2)Water requirement per kg of product

(liters/kg)

Potatoes 350-625 500-1500

Wheat 450-650 900-2000

Rice 500-950 1900-5000

Sorghum 1100-1800

Soybeans 450-825 1100-2000

Sugarcane 1000-1500 1500-3000

Chicken 2500-5700

Cotton 550-950 7000-29000

Beef 1000-100000 15000-70000

Freshwater Requirements for Different Agricultural Products

• Agricultural chemicals– Effects

• Direct & indirect– Biomagnification

• Soils and weather

USDA Photo



• Pesticides– Chlorinated hydrocarbons

• E.g., DDT & Dieldrin

– Organophosphates• E.g., Malathion

– Carbamates• E.g., Fenoxycarb

– Pyrethrins

– Direct & indirect effects

(Alton N. Sparks, Jr., The University of Georgia, www.forestryimages.org)


• Herbicides– Pros & cons

– E.g., Agent Orange & Round-up

• Range management?

(Tom Landis, USDA Forest Service, www.forestryimages.org)


• Fertilizer– Direct & indirect effects

– Pros & cons

(Scott Roberts, Mississippi State University, www.forestryimages.org)



• Control measures?


• Agrichemicals– Integrated pest management– Organic farming– Reduce need for chemical fertilization

• Rotate crops• Cover crops• Manure spread

– Reduce runoff– ?

• Management of streams, ponds, & wetlands– Fencing– Alternative water sources– Erosion & sedimentation


• Water management– Crop irrigation– Livestock

USDA photo by: Tim McCabe



• Livestock: grass fed vs. feed lot

• Grazing– Vegetation– Soils– Aquatic and riparian systems


Water Issues & Agrichemicals Often linked Water issues also include sedimentation, turbidity, O 2...

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