Keith O. Keplinger

Limiting pumping from the Edwards Aquifer: An economic investigation of proposals, water markets, and spring flow guarantees

The Edwards Aquifer, near San Antonio, Texas, is an important water source for both pumping and spring flow, which in turn provides water for recreation and habitat for several endangered species. A management authority is charged with aquifer management and is mandated to reduce pumping, facilitate water markets, protect agricultural rights, and protect the species habitat. This paper examines the economic dimensions of authority duties. A combined hydrologic-economic model is used in the investigation. The results indicate that proposed pumping limits are shown to have large consequences for agricultural usage and to decrease the welfare of current aquifer pumping users. However, the spring flow habitat is found to be protected, and the gains from that protection would have to exceed pumping user losses in order for the protection measures to increase regional economic welfare. Agricultural guarantees are shown to cause use value differences, indicating the opportunity for emergence of an active water market. Fixed quantity pumping limits are found to be an expensive way of insuring adequate spring flow.

Simulation of Nutrient Losses from Chicken Litter Applications in East Central Texas with APEX and SWAT

An increase in broiler chicken production has recently occurred in the Brazos-Navasota River Watershed (BNRW) in east central Texas. At present, over 8 million broiler chickens are produced annually in the Duck Creek Watershed (DCW), the most intensive production area of any of the BNRW sub-watersheds. Concern exists regarding the potential degradation of water quality within the BNRW due to nutrient runoff from land-applied broiler litter. Thus a simulation study was initiated to determine the potential impacts of current and alternative litter management practices. The application of Agricultural Policy eXtender (APEX) and the Soil and Water Assessment Tool (SWAT) models to assess water quality impacts for DCW baseline (current) conditions is reported here. The results of two simulation approaches are described: APEX run in combination with SWAT and SWAT without APEX.

Economic and Environmental Assessment of Proactive Phosphorus Control Measures for Broiler Operations

Duck Creek watershed, a small watershed in east-central Texas, experienced an influx of broiler growing operations in the later half of the 1990s. Preliminary results indicated that year 2000 levels of broiler litter land application do not pose a water quality concern but that a significant expansion of broiler production would more than double ambient phosphorus loads in the watershed. Environmental and economic modeling were used to assess the effects of phosphorus control measures designed to proactively mitigate the environmental impacts from further broiler industry expansion. Results of best management practice (BMP) simulations indicate that ambient phosphorus loads from broiler litter can be reduced by reducing the rate of litter application, by hauling off litter, by adding phytase to broiler feed, and by amending broiler litter with aluminum sulfate (alum). Reduced-rate scenarios were substantially more cost-effective than haul-off scenarios. Simulations of the phytase and alum BMPs produced net economic benefits in addition to reducing phosphorus loads. Model results thus indicated that relatively low-cost BMP options or ones yielding net monetary benefits (e.g., phytase and alum) would protect water quality in Duck Creek in the event of a low, moderate, or even a very significant expansion of the regional broiler industry. Subsequent to this research, the broiler integrator conducted field trials that confirmed the economic benefits of phytase but not alum. Alum addition did not produce the expected economic benefits, primarily because of the regional climate, which differed from that assumed in the analysis.

Impacts of Livestock Concentration and Application Rate Restrictions on Manure Utilization

A key factor motivating high manure application rates is the spatial concentration of livestock facilities, which has substantially increased in recent decades. Greater manure production in a given region creates incentives to over apply manure near livestock facilities in order to avoid high hauling costs. A manure transportation and application model (MTA) was developed to simulate manure application behavior. The model was populated by average national (USA) values for four types of manure for nutrient content, application and hauling expense, crop distributions, crop nutrient removal rates, and other agronomic parameters. The first set of model simulations allowed manure application at the higher of the N-rate or P-rate (high agronomic rate). Model results generally illustrate the diseconomies of manure production, e.g., marginal manure value decreased and maximum manure hauling distances increased as manure availability increased. The model also simulated increasing rates of excess phosphorus application (amounts exceeding crop removal) as manure availability increased. To explore the economic impacts of eliminating excess nutrient applications, MTA was rerun with a constraint limiting manure application to the lower of the N-rate or P-rate (low agronomic rate). Although less commercial fertilizer was required for low agronomic rate scenarios, hauling and application costs increased, such that the net cost of switching from a high to a low agronomic application rate increased at an increasing rate as manure availability increased. In summary, model results indicate that as livestock concentrations increase, there are diseconomies to manure utilization, more excess nutrients are applied, and reducing manure application rates becomes more expensive.