FARMING AND IRRIGATION


POTENTIAL WATER QUALITY PROBLEMS

Farming and irrigation can cause water quality problems by increasing sediment, nutrients and herbicide/pesticide concentrations.  In addition, removal of surface water for irrigation sometimes reduces stream flows to the point that water quality and aquatic life are impacted. 

Increased sediment concentrations in waterbodies can impact fisheries and other aquatic life. This may include: less successful spawning activity; a change in the macro-invertebrate populations; and a change in the aquatic plant community.  In addition, overgrazing can increase water temperature if riparian plant species that normally provide shade are eliminated.

Increased nutrient concentrations can cause over fertilization of waterbodies creating a condition known as eutrophication.  This situation, which is often more serious in lakes than streams, results in excessive algal growth.  When the algae die and decompose, oxygen is depleted.  Depending on the extent of the oxygen depletion, a fish kill may result.  Increased nutrient levels can also impact water supplies that are used for human consumption. Elevated nitrate levels can interfere with the blood's ability to carry oxygen.  This can be a serious problem for infants and the elderly.  

Increased herbicide/pesticide concentrations can impact aquatic life.  Depending on the type of herbicide/pesticide, a number of human health problems are possible.

CRITICAL AREAS AND ISSUES

The closer the agricultural activity is to a surface waterbody or ground water source, the greater the chance for a water quality impact.  While this is a general rule of thumb, it is possible that areas close to water may not have an impact and areas removed from water may have a significant impact.  

When identifying critical areas, it is important to consider: soil type; topography; crop type; drainage patterns; off season cultivation practices; depth to ground water; irrigation practices; and precipitation patterns.  Situations that can have a negative impact on water quality include: irrigation return flows; cultivation of steep slopes; over use of herbicides/pesticides; over fertilization; long periods of heavily tilled bare soil; and row crops on sloped terrain.  

A number of farming and irrigation management tools can be used to protect water quality.  They are outlined in the 'Making Improvements' section below.   However, before improvements are planned existing conditions should be assessed.

ASSESSING EXISTING CONDITIONS

One of the best sources of information for assessing existing conditions is provided by the Natural Resources Conservation Service (NRCS).  NRCS personnel are available to help develop a conservation plan that is tailored to a specific operation.  Alternatively, producers can complete a self assessment by utilizing tools such as the Farm/Ranch Assessment Worksheet for Cropland that was recently developed by NRCS and the National Association of State Departments of Agriculture.  The worksheet ranks numerous environmental and operational factors on a scale of 1 to 4 with 4 being best.  It can be used in conjunction with the information provided in the accompanying web site or it can be used as a stand alone indicator of areas that need improvement.

While assessment tools differ, generally there is a potential to cause environmental or human health problems if any of the following exist:

  • The farm has surface waterbodies located within its boundaries, or drainage patterns carry runoff from the farm to nearby surface waterbodies.
  • Areas of the farm have a high ground water table.
  • Areas of the farm have erosive soils on sloped terrain and those soils are row cropped or lay bare for part of the year.
  • There is noticeable sheet, rill or gully erosion.
  • There is noticeable stream bank erosion.
  • Irrigation runoff is allowed to enter a surface waterbody. 
  • Areas of the farm with a high ground water table are irrigated.
  • Areas of the farm with a high ground water table have fertilization and herbicide/pesticide application rates that are not carefully managed.
  • Grazing livestock are allowed direct access to a surface water body (see grazing).
  • Runoff from feedlots is allowed to enter a surface waterbody or the feedlot is located in an area with a high ground water table (see feedlots).

MAKING IMPROVEMENTS

Improvements, often called Best Management Practices (BMPs), fall into two broad categories: structural or management. A good conservation plan often contains both types of BMPs.

There are many kinds of structural BMPs including: fencing; culverts; bridges; dikes; rip-rap; sediment basins; runoff diversion channels; land leveling; filter strips; irrigation systems;  watering facilities; etc. Depending on complexity, a structural BMP may require a detailed engineering drawing.  In some cases, existing drawings can be utilized or modified to fit a given situation. 

Management BMPs include: reduced tillage; crop rotation; cover crops; strip cropping; crop selection; irrigation management; nutrient management; herbicide/pesticide management; etc.  Management BMPs often require attention to detail such as carefully monitoring soil moisture to reduce irrigation runoff or keeping precise records of herbicide/pesticide application rates to facilitate fine tuning.  Because they do not include a structural component, direct costs are often less than for structural BMPs.  However, there may be an ongoing labor cost for as long as the practice continues.    

Excellent sources of information for planning specific BMPs include:

FUNDING AND TECHNICAL ASSISTANCE

Section 319 funds are available from DEQ to assist with conservation practices on private cropland.  Applicants for these funds must show that a water quality problem exists and that the proposed practices will improve the problem. Interested parties should apply through their local conservation district.  The NRCS may have funds available through the Environmental Quality Incentives Program.  The Wyoming Game and Fish Department has funds for practices that benefit fisheries.

Technical assistance is available from local conservation districts, the Natural Resources Conservation Service, and the Cooperative Extension Service.  The Internet also contains a wealth of information including the following sites:

NPS Home | Identify Problem | Set Objectives | Plan BMPs | Obtain Funds | Implement BMPs | Evaluate