The North Platte, Natural Resources District has established the Lisco-Oshkosh- Lewellen (LOL) Groundwater Quality Sub-Management Area in parts of Garden and Morrill Counties. The LOL sub-area consists of a strip of land along the north side of the North Platte River ranging in width from 2 miles to about 5 miles. The western boundary of the Sub-area is about 3 miles west of Lisco, and the eastern boundary of the sub-area is at the Garden-Keith County line East of Lewellen. This GWSMA aims to protect the quality of groundwater and reduce Nitrate levels in groundwater resources. Nitrate is a colorless and odorless inorganic compound that can harm human health in high concentrations. It naturally occurs in soils and groundwater but can be affected by nitrogen leaching from farming practices and livestock waste. Producers in the LOL sub-area are required to comply with level 2 regulatory controls adopted by the North Platte NRD and approved by the Nebraska Department of Natural Resources. The LOL sub-area was adopted in October 1999.

Keeping Drinking Water Safe

The U.S. Environmental Protection Agency has established a maximum contaminant level (MCL) of 10 parts per million nitrate as nitrogen in drinking water. In the Lisco-Oshkosh-Lewellen Sub-Area, about 40% of the wells tested periodically by the NRD are 10ppm or above. A study conducted for the NRD by the University of Nebraska-Lincoln Conservation and Survey Division, published in 1990, identified the source of the nitrate as fertilizer that had leached from corn fields overlying the shallow groundwater aquifer.

Level 2 Regulatory Controls

Farmers in the Lisco-Oshkosh-Lewellen Groundwater Management Sub-Area are required to comply with Level 2 regulatory controls, which are intended to improve the management of fertilizer and irrigation water in the area. These controls include:

  1. Beginning May 1, 2001, approved water-measuring devices will be required for all irrigators, including groundwater (well) irrigators and surface water (ditch) irrigators. Measuring devices must meet specifications and be kept in working order. The North Platte NRD will provide cost-share to reimburse farmers 50 percent, up to $625.00, of the cost of installing water-measuring devices.
  2. Fields that are smaller than 5 acres and are planted to a crop other than corn are exempt from 2 and 3.
  3. Flow meter readings from the beginning and end of the irrigation season and the total amount of water applied; dates and amount of water applied each irrigation and method of irrigation scheduling used; actual yield of present year’s crop and planned crop rotation for the following year.
  4. No annual report to the North Platte NRD required
  5. Ban on fall and winter applications of commercial fertilizer (after September 1; wheat and other small grains exempted.)

Regulatory controls include practices that will help farmers determine how much fertilizer they need and thus avoid overfertilizing. But controls also include practices aimed at allowing farmers in the sub-area to improve irrigation management. Water, especially irrigation water, is the means by which nitrate is carried from the crop’s root zone to the underlying groundwater. Thus, to avoid nitrate leaching, both nutrient (fertilizer) management and irrigation management are necessary. The LOL sub-management area is susceptible to groundwater contamination because of the presence of irrigated agriculture, the shallow depth of groundwater, and the presence of sandy soils. This designation was determined by the USGS/ UNL hydrologic study presented in 1990.


These links lead to several extension publications on the importance of managing both nitrogen and irrigation water to avoid nitrate contamination:


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