| Four management alternatives which restrict the use of water and one that imposes a moratorium on new irrigation development were compared with the options of allowing irrigators unrestricted use of ground water in east central Nebraska. The objectives of this study were to evaluate the impacts of options on farm level income, on aggregate farm income and on the aquifer. A recursive, polyperiod linear program formed the basis of the farmer's decisions. The model was structured to determine how producers might respond to three-year allocations. The polyperiod component reflected the opportunity cost of using water in year one rather than year two or three. It was recursive to allow for reflection of the impact of actions in earlier years on costs in subsequent years. Producers were assumed to plan based on expected average values but could adjust their intentions according to the weather conditions.;The study area was divided into three regions based on hydrologic conditions, with a model farm representative of each region. Region 1 had abundant ground water with well capacities of at least 750 gallons per minute (GPM) and at least 150 feet of saturated thickness. Region 2, a poor hydrologic region, had well yields of less than 750 GPM and less than 150 feet of saturated thickness. Region 3 had the potential of developing ground water problems with greater than 750 GPM well yields, but less than 150 feet of saturated thickness.;The cropping pattern response to water restrictions was similar across all regions. Part of the land developed for irrigation was planted in dryland grain sorghum so that the rest of the land could be in corn and soybeans, irrigated as close to the full irrigation level as possible.;The impact of the different options on the aquifer varied according to the initial aquifer conditions. Region 1 was affected primarily in terms of reduced pumping lifts, with minor increases in well yields. Region 2 was most significantly impacted in terms of extension of aquifer lift, with minor impacts on pumping lifts and well yields. In Region 3 the impact of limiting water resulted in reduced pumping lifts and greater well capacities as well as extension of aquifer life.;A 400-node, three dimensional finite element hydrologic ground water model was used to simulate the impact of annual pumpage on the aquifer. New pump costs were estimated annually to reflect changing aquifer conditions.;In all regions, a 10-inch allocation was found to have the highest net returns over time for the model farm, but surprisingly the net returns were close across all options. Aggregate farm income was close across most options but with greater differences than occurred in the model farm. In Regions 1 and 3 the highest income option was a 10-inch allocation, improving net returns by... |
