Master of Arts / Department of Sociology, Anthropology, and Social Work / Matthew R. Sanderson / Depletion of the Ogallala Aquifer is a significant concern for many communities in the High Plains region and, indeed, the global food system. Using data from 181 counties in the High Plains region, the STIRPAT model is used to identify the social drivers of groundwater depletion. The ordinary least squares regression analysis indicates that the scale of irrigation, value of agricultural commodities, and farm income each increase depletion levels, while county per capita income is negatively associated with depletion. Results from a path analysis reveal that government subsidies indirectly drive groundwater depletion by supporting farm incomes and the value of commodities. Groundwater depletion in the High Plains region is ultimately a policy decision − one that has generated a positive feedback loop linking farm incomes to groundwater withdrawals.

Doctor of Philosophy / Department of Agronomy / P.V. Vara Prasad / The Ogallala Aquifer is a large underground water source located under the High Plains and is used as the primary irrigation source for producers in the region. Hyper-extraction of the Ogallala is causing a reduction in irrigation capacity for a large part of the region. Confined animal feeding operations in western Kansas rely upon irrigated crops, mainly corn [Zea mays (L.)] as a source of feed. Research has shown that forage sorghum [Sorghum bicolor (L.) Monech] could meet the demands of the confined animal feeding operations while using less water than corn. An experiment was designed to evaluate corn and forage sorghum in Western Kansas. The objective of this research was to evaluate the water use and growth characteristics of irrigated and dryland corn and forage sorghum. Field experiments were conducted at two locations (Tribune Experiment Station, Tribune and a cooperator’s field near Hoxie, Sheridan County Kansas) in 2011-2013. The experimental design at Tribune was a randomized complete block with four replications. A traditional replicated design was not possible at Hoxie. Multiple subsamples per plot were obtained and data are reported as means with standard errors. Corn and forage sorghum were grown under both dryland and fully irrigated conditions at both locations. Neutron access tubes were installed to monitor soil water. Aboveground biomass, intercepted solar radiation and volumetric soil water content were recorded at 5 sampling dates each growing season. Water use was similar between irrigated corn and forage sorghum. There were differences in biomass from year to year between the irrigated crops. Dryland water use was similar between the two crops and also had differences in biomass from year to year. Yields were significantly lower than average for all crops in 2012 due to drought conditions. Solar radiation interception correlated with aboveground biomass measurements. Aboveground biomass from the forage sorghum and corn was ensiled both years and analyzed for nutrient composition. This research suggests that forage sorghum silage may be an acceptable replacement for corn silage in areas with reduced irrigation capacities.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Aleksey Y. Sheshukov / Isaya Kisekka / The Ogallala aquifer has been important to agriculture in the U.S. High Plains for the past six decades. Groundwater from the aquifer helped turn the fertile soils of the region, large parts of which are semi-arid, into some of the most productive agricultural lands in the U.S. and the world. However, this agricultural success has come at a great cost to the aquifer. Today, as a result of drastic aquifer drawdown, well capacities in some regions of the High Plains are no longer sufficient to sustainably irrigate crops. In response to this growing problem, wide ranging efforts towards conservation of the Ogallala aquifer were formulated and implemented. One of these efforts is to further improve irrigation efficiency. Adaptation of microirrigation, an efficient method of irrigation, to center pivots is regarded by some as the next major step towards expanding the usage of microirrigation technology, and along with-it improving the efficiency in center pivot systems. Four studies were conducted as parts of this dissertation with the application of a four-span center pivot, installed at the Kansas State University’s Southwest Research and Extension Centre (SWREC) in Garden City, Kansas. The studies assessed the technical performance of Mobile Drip Irrigation (MDI) compared to Low Elevation Spray Application (LESA) and Low Energy Precision Application (LEPA). In the first study, the irrigation uniformity, application efficiency and seasonal irrigation uniformity of MDI were evaluated against those of LEPA and LESA. Two sets of MDIs, one with a dripper flow rate of 3.8 L/h, and another of 7.6 L/h, a LESA spray and LEPA bubbler were utilized. Potential differences in season-long irrigation uniformity between the devices were evaluated by analyzing a periodically acquired vegetative index data from aerial imaging. The results showed that MDI and LEPA were more efficient than LESA as indicated by their significantly higher coefficients of uniformity and higher application efficiencies. The second study evaluated soil water redistribution under MDI against those of LEPA and LESA. The effect of irrigation was found to be mostly limited to the top 60 cm of the soil profile for all the evaluated irrigation application technologies. MDI and LEPA showed the highest horizontal variation in water content, and water redistribution pattern of MDI was similar to LEPA. In the third study, the performance of MDI for corn production, in comparison to LESA and LEPA was conducted by comparing grain yield, water productivity, above ground biomass, leaf area index (LAI), and soil water content. In general, crop biophysical measurements under MDI were not significantly different from those under LEPA and LESA, and any marginal benefits of MDI were likely masked by rainfall. Hence, further evaluation of MDI is recommended under stringent water application conditions. The fourth study assessed MDI dripline spacing and length for different soil types.

Functional morphology and morphometric studies on various mammalian groups have shown marked differences in crania and mandible shape based on dietary preferences and feeding habits. In this study I used three-dimensional geometric morphometric methods to measure the shape of crania and mandibles of herbivorous and omnivorous mammals from three formations in northwestern Nebraska to explore the structure and disparity of ecosystems through time: The White River Group (Chadronian/Orellan/Whitneyan), the Arikaree Group (Arikareean), and the Ogallala Group (Hemingfordian/Barstovian/Clarendonian). Throughout the time period compromising these formations the climatic conditions were becoming more arid, grasslands were expanding and the large mammalian faunal compositions were shifting from browser dominated to grazer dominated. Relative warps analysis show a visible separation of faunas between the three formations that cannot be attributed to phylogeny in plots based on either the crania or the mandibles. Phylogenetic effects were taken into account using generalized least squares. These results indicate that it may be possible to differentiate fossil taxa from different formations and environments based on the shape of cranial and mandibular elements as well as to infer the environment or diet of a fossil if other unequivocal data are not available.

Master of Science / Department of Civil Engineering / David R. Steward / A one-dimensional model was developed to study the flow of groundwater in the sloping Ogallala Aquifer at a steady state during predevelopment condition. The sloping base was approximated using a stepping base model. GIS applications were applied during data collection and preparation, and later during interpretation of model results. Analytical and numerical methods were employed in the development of this model which was used to try to understand long-term water balance in the study region. The conservation of mass was achieved by balancing groundwater input, output, and storage; this led to understanding the interactions of groundwater and surface water in the predevelopment conditions. The study resulted in identification of where natural discharge from groundwater to surface water occurred, and the quantity of these flows was obtained. The Ogallala Aquifer is thick in the south western part of Kansas, this region had an average saturated thickness of 100m during predevelopment conditions. The model found that groundwater flowed at a discharge per width of approximately 17 m[superscript]2/d in this region. The aquifer thickness tends to gradually decrease from west to east and from south to north. The northern part had an average saturated thickness of 40m during predevelopment conditions; the model found that groundwater flowed at a discharge per width of approximately 3 m[superscript]2/d in this region. It was also found that groundwater leaves the Ogallala Aquifer on the eastern side with discharge per width between 0-3 m[superscript]2/d. The discharge from groundwater to surface water was summed over contributing areas to river basins. The discharge to streams necessary to satisfy long-term conservation of mass computed by the model showed that Cimarron River has total baseflow of about 5.5 m[superscript]3/s; this was found to be almost 100% of the total streamflow recorded during predevelopment conditions. The Arkansas River was found to have total baseflow of about 0.97 m[superscript]3/s, which is approximately 14.3% of the total streamflow recorded during predevelopment conditions. The Smoky Hill River was found to have total baseflow of about 1.7 m[superscript]3/s, which is approximately 73.9% of the total streamflow recorded during predevelopment conditions. The Solomon River was found to have total baseflow of about 0.95 m[superscript]3/s, which is approximately 41.1% of the total streamflow recorded during predevelopment conditions. The Saline River was found to have total baseflow of about 0.25 m[superscript]3/s, which is approximately 62.5% of the total streamflow recorded during predevelopment conditions. The Republican and Pawnee River was found to have total baseflow of about 0.38 m[superscript]3/s and 0.22 m[superscript]3/s, which is approximately 18.5% and 12.6% of the total streamflow in the predevelopment conditions respectively. The model was found to be always within -16 to +12 meters between observed values and the model results, with an average value of 0.15m and a root mean square error of 1.98m. Results from this study can be used to advance this study to the next level by making a transient model that could be used as a predictive tool for groundwater response to water use in the study region.

Master of Science / Department of Civil Engineering / David R. Steward / Kansas relies on groundwater for nearly 85 percent of the total water used each year, most of which is used for irrigation. Over the last 30 years, declining groundwater levels in some areas have put pressure on agricultural industries. Ongoing research on the usage of groundwater resources will be necessary to sustain agriculture. In this study, two groundwater models were developed to investigate groundwater availability and use in western Kansas. The first model, called the Saturated Thickness Model (STM), investigated how groundwater resources will change over the next century. The second model, called the Change in Water Level Model (CWLM), was used to forecast water use trends for three agricultural districts in western Kansas by relating the change in groundwater levels over time to the volume of water pumped for irrigation. To understand how these changes would affect the agricultural industry, the research investigated historical trends in reported groundwater use, corn production and cattle in feedyards. The results showed significant decreases in the modeled saturated thickness over the next 100 years in western Kansas. Modeled groundwater use matched reported groundwater use data relatively well. The model showed significant decreases in groundwater use over the next 100 years, with the largest decrease being in the southwest district. Overall, forecast water use trends were in agreement with current outlooks for each area. The results from the correlation analysis showed a negative relationship between groundwater use and irrigated corn production, indicating improved irrigation efficiency and crop species over the past 30 years. Further correlations showed the number of cattle on feed in a particular area increased with the amount of irrigated corn production in the same area. This implies the cattle feedyards tendency toward local source of grain. As groundwater resources decline, corn production will decrease, and changes in the agricultural landscape will require adaptation. Feedyards will need to find new sources of corn grain or change to a less water dependent feed. Further research is needed to determine where corn grain will be produced in the next 100 years, and how corn grain will be transported to feedyards in southwest Kansas.

Typescript (photocopy). / Digitized by Kansas Correctional Industries / Department: Economics.

Master of Agribusiness / Department of Agricultural Economics / Bill B. Golden / While Kansas, and specifically western Kansas, are known by many to be the backbone of agriculture in our nation, much of that productivity has been built on the heels of the invention and efficiency of irrigation technology. Unfortunately, recharge and replenishment of the High Plains - Ogallala Aquifer has not kept pace with the demands of agricultural production, and current indications state that without the implementation of conservation or management practices that the aquifer in Kansas could be depleted by 2060 (Steward, et al. 2013). The producers of Kansas are committed to long-term solutions to preserve their way of life, espouse their commitment to natural resources and the environment, and ensure the viability of their operations for years to come. This study analyzed the economic impact of a proposed Local Enhanced Management Area (LEMA) for Groundwater Management District ¬(GMD) #4. While there currently is a LEMA in a portion of GMD #4 known as the Sheridan 6 LEMA, the board of GMD #4 has initiated the process to institute a district-wide LEMA that would affect a large portion of the 10-county area of the groundwater management district (Cheyenne, Rawlins, Decatur, Sherman, Thomas, Sheridan, Graham, Wallace, Logan, and Gove Counties). To complete the analysis for the proposed policy change, multiple scenarios were derived using the IMPLAN software. The first model serves as the baseline scenario and provides status quo information on the current irrigated cropping economics of GMD #4. The second scenario assumes that a district-wide LEMA would require a 25% reduction in groundwater use, compared to current irrigation practices. To achieve this reduction in groundwater use, irrigated acreage was reduced by 25% and transitioned to dryland production. For the third and final scenario, an optimal irrigated crop-mix ratio is determined based on the current shift in production as reported by the producers in the Sheridan 6 LEMA. While this scenario does not reduce irrigated acres, it shows the economic gains that can be captured by using less water-intensive crops as part of the crop-mix ratio. The reduction in irrigation is also imbedded in that the acreage in which production is shifted away from is more water intensive towards acreage that is less water-intensive. Due to a reduction in groundwater use for irrigation, the study determined that there is a negative economic impact in relation to employment and total output in the GMD #4 area. There are 173 less individuals employed from the 25% reduction in groundwater use. Additionally, direct output is reduced by $44.6 million and total output is reduced by $60.0 million. This equates to a $194.49 reduction per acre on a per-acre basis. The study further showed that the economic impact could be lessened by the use of a crop-mix shift as evidenced in the current Sheridan 6 LEMA. The assessment of a crop-mix shift decreased the loss of direct output by $12.0 million to $265.0 million and total output by $16.5 million to $357.1 million. On a per-acre basis, this is a reduction of $140.97, or mitigation of $53.52 in loss per acre due to the use of an optimal crop-mix shift. While agricultural production is highly dependent on many factors, it can be universally agreed that the landscape of agriculture would be different if water was not an available resource. It is the hope that this research will provide a starting point for the producers of GMD #4 to have a conversation about the economic costs associated with the implementation of a LEMA, as well as discuss other options and opportunities to make educated, well-informed decisions that are impactful both now and for generations to come.

Groundwater-derived phosphorus has often been dismissed as a significant contributor towards surface water eutrophication, however, this dismissal is unwarranted, making the quantification of phosphorus concentrations in groundwater systems immensely important. Machine learning models have been employed to quantify the concentrations of various contaminants in groundwater, but to our best knowledge have never been used for the quantification of groundwater phosphorus. The goal of this research was to use a boosted regression tree framework to produce the first believed machine learning model of phosphorus variability in groundwater, with the High Plains aquifer serving as the study area. Results display a boosted regression tree model that was not capable of explaining and predicting the statistical variance of phosphorus throughout the aquifer under standard conditions, however important variable correlation data that can potentially be incorporated into future studies that aim to further understand phosphorus dynamics in groundwater was obtained from this research.

Master of Arts / Department of Sociology, Anthropology, and Social Work / Laszlo Kulcsar / Environmental, economic and social conditions have changed drastically throughout Great Plains farming communities. In Southwest Kansas, the Ogallala Aquifer supports extensive agricultural industries and family farms through hyper-extraction of groundwater resources. Capitalistic ventures in farming have led to socials changes like declining community populations, out-migration of youth and family farm transformations. The relationship between environmental change, economic development and social changes is explored through a case study of Haskell County Kansas. Interviews were conducted to understand residents' perspectives of declining environmental resources available to achieve continued economic development by way of family farming. Residents also explain social changes that have resulted from evolving economic conditions and increasing use of groundwater resources.