VTechWorks Repository :: Browsing by Author "Cobourn, Kelly M."

Browsing by Author "Cobourn, Kelly M."

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Air quality economics: Three essays
Yao, Zhenyu (Virginia Tech, 2022-06-17)
This dissertation consists of three separate research projects. Each paper uses a different applied econometric technique to investigate problems related to air quality economics. The first chapter is a general introduction to all three studies. The second chapter explores adopting an environmentally-friendly public transportation system in Europe. The Bayesian econometric methods show that willingness to pay for a new public transportation system is primarily driven by improvements to public goods, such as air quality and greenhouse gas emission reduction. The third chapter uses the red tide-related stated experience and satellite imagery of chlorophyll-a concentration as well as field data of respiratory irritation. This chapter illustrates that ancillary scientific information can be efficiently combined with choice experimental data. The fourth chapter uses panel fixed-effect models to investigate the short-term effect of air pollution on students' cognitive performance in China. It is shown that PM2.5 has a significantly negative impact on students' exam performance.
Assessing the extent and drivers of forest plantation establishment in Andhra Pradesh
Wynne, Randolph H.; Thomas, Valerie A.; Gundimeda, Haripriya; Amacher, Gregory S.; Cobourn, Kelly M.; Köhlin, Gunnar (2017-07)
Assessment of silvicultural practices to improve survival and growth of pioneer and mid-successional hardwoods on old field restoration sites
Steele, Jason Keith (Virginia Tech, 2020-07-01)
Survival and growth of planted trees are common indices used to evaluate success of wetland restoration efforts used to compensate for wetland losses. Restoration efforts on marginal agricultural lands typically result in less than satisfactory survival and growth of desired tree species. This study evaluated seed source ecotype, greenhouse preconditioning and combinations of five mechanical site preparation techniques (mound, bed, rip, disk, pit), four levels of planting stock (gallon, tubeling, bare root, and direct seed), and three planting aids (mat, tube, none) on the survival and growth of American sycamore (Platanus occidentalis L.) and willow oak (Quercus phellos L.) planted on an old field riparian area in the Virginia Piedmont. American sycamore seedlings subjected to greenhouse flood preconditioning had 25% greater height and willow oak seedlings grown under normal greenhouse conditions had 18% greater diameter, but these greenhouse adaptations did not confer greater survivability or growth after field planting. American sycamore seeds sourced from dry ecotypes were 14% taller than wet ecotype seeds, and willow oak acorns sourced from wet ecotypes were 11% taller than dry ecotype acorns, indicating that parental ecotype may influence survivability and growth. The combination of mounding site preparation and gallon planting stock increased mean survival to 100% and aboveground dry biomass (5.44 Mg/ha/yr) in American sycamore. Willow oak had 45% greater woody stem volume with mounding site preparation 80% greater woody stem volume with gallon and bare root planting stock. Tubeling planting stock provided significant benefit relative to the low planting stock cost for American sycamore, while bare root seedlings were shown to be an effective planting stock for willow oak. The use of appropriate ecotype seed sources, use of mounding mechanical site preparation techniques and planting of species appropriate planting stock increased survival and growth of common early and mid-successional Piedmont tree species on marginal agricultural lands. Treatments that appear to be economically viable for restoration and mitigation efforts could potentially offer other economic incentives such as short rotation woody crops and timber value, which might induce additional private landowners to attempt restoration efforts in marginal old field riparian areas.
Characterizing the impact of climatic and price anomalies on agrosystems in the northwest United States
Wurster, Patrick; Maneta, Marco; Begueria, Santiago; Cobourn, Kelly M.; Maxwell, Bruce D.; Silverman, Nick; Ewing, Stephanie; Jensco, Kelsey; Gardner, Payton; Kimball, John; Holden, Zachary; Ji, Xinde; Vicente-Serrano, Sergio M. (2020-01-15)
We present an analysis of the sensitivity of three key crops (alfalfa, barley and winter wheat) produced in the northwestern United States to climatic and agricultural market anomalies using widely used standardized indices. Rather than investigating sensitivity of crop yields (production per unit area), we focus on agricultural production (yield * harvested area) anomalies, which captures both variations in yield and the effect of decision-making factors such as allocation of cropping area. We used two well-known standardized precipitation and reference evapotranspiration (ETo) indices (SPI and EDDI, respectively) and a standardized crop value index in a multivariate linear regression analysis to determine the characteristic timing and time-scales of precipitation and ETo anomalies that best explain annual crop production anomalies. Since climatic and market factors are standardized, regression coefficients are interpreted as a sensitivity measure that captures the relative effect of climatic and agricultural markets on agricultural production. Results show that alfalfa production was most sensitive climatic anomalies while barley and wheat production was more responsive to crop prices. Sensitivity to precipitation anomalies followed gradients in precipitation, temperature, and soil moisture regimes across the study area where drier and warmer climates were associated with increased sensitivity to climatic anomalies. We found that irrigation decoupled alfalfa production from climatic variability, but the effect of irrigation on decoupling barley production was less clear. Winter wheat production was most sensitive to price anomalies, and alfalfa was least sensitive. Omitting agricultural market conditions and other farmer incentives may introduce biases in our understanding of how drought and climate change impact agricultural production.
Cooperative Management of Invasive Species: A Dynamic Nash Bargaining Approach
Cobourn, Kelly M.; Amacher, Gregory S.; Haight, Robert G. (2019-04)
We use a Nash bargaining framework to examine scope for bargaining in invasive species problems where spread depends on the employment of costly controls. Municipalities bargain over a transfer payment that slows spread but requires an infested municipality to forgo nonmarket benefits from the host species. We find that when the uninfested municipality has a relative bargaining power advantage, bargaining may attain the first-best solution. However, in many cases a short-term bargaining agreement is unlikely to succeed, which suggests a role for higher levels of government to facilitate long-term agreements even when the details are left to municipalities to negotiate.
Drivers of Forest Plantation Establishment in Andhra Pradesh
Wynne, Randolph H.; Thomas, Valerie A.; Gundimeda, Haripriya; Amacher, Gregory S.; Cobourn, Kelly M.; Köhlin, Gunnar (2018-05-30)
Conclusions
Plantation forestry rapidly expanding in Asia

Small spatial extent and rapid harvest-regeneration cycle present interesting — but resolvable — remote sensing challenges

Understanding the drivers and ramifications of these new trees outside forests vital
Erratum: Chance, E.W., et al. Identifying Irrigated Areas in the Snake River Plain, Idaho: Evaluating Performance across Compositing Algorithms, Spectral Indices, and Sensors. Remote Sens. 2017, 9, 546
Chance, Eric W.; Cobourn, Kelly M.; Thomas, Valerie A.; Dawson, Blaine C.; Flores, Alejandro N. (MDPI, 2017-07-18)
In the published paper [1], the title and Appendix Tables A4, A5, A7, and A8 contain typographical errors. The correct title and table captions are as follows: [...]
Essays in Suface Water Quality Valuation
Swedberg, Kristen M. (Virginia Tech, 2024-05-29)
This dissertation is comprised of three essays examining methods for surface water quality valuation. The first essay uses Zillow's ZTRAX property transaction database to investigate variation in hedonic price effects of water clarity on single-family houses throughout the United States. I consider five spatial scales and estimate models using different sample selection criteria and model specifications. The results indicate considerable spatial heterogeneity both within and across the four U.S. Census regions. However, I also find heterogeneity resulting from different types of investigator decisions, including sample selection and modelling choices. Thus, it is necessary to use practical knowledge to consider the limits of market areas and to investigate the robustness of estimation results to investigator choices. In the second essay, I integrate a coastal recreation demand model for Southern New England with property sales in Massachusetts and Rhode Island to estimate the impacts of water quality improvements for freshwater and saltwater resources throughout the region. While traditional hedonic studies for water quality reveal the direct effects of local water quality on housing prices, the spatial extent of the models is limited to 2 km from the waterfront. Integrating recreation demand models with hedonic models allows identification of additional indirect effects of water quality at recreation sites that are capitalized in housing markets through a recreational index (i.e., the potential recreational benefits for a neighborhood). However, the spatial extent of these models is currently untested. I compare the spatial extent of indirect and direct effects of water quality for multiple water quality inputs isolating spatial and temporal sources of variation. The results indicate heterogeneity in the direct effects of freshwater and saltwater clarity depending on whether the source of variation is spatial or temporal. Conflating spatial and temporal water quality variation can lead to anomalous conclusions on the impacts of coastal recreation on housing markets. In the third essay, I evaluate meta-regression models (MRMs) that are used by policy makers in calculating the potential benefits of improvements in environmental quality resulting from proposed regulatory actions. MRMs lay the foundation for benefit transfers applied by EPA to recent rulemakings under the Clean Water Act (CWA) in addition to other environmental contexts (e.g., health benefits under the Clean Air Act). While recent literature has emphasized the necessity that MRMs satisfy key theoretical conditions, including scope sensitivity and the adding up condition, existing MRMs that fulfil these properties require imposing structural model restrictions or removing relevant explanatory variables from the MRM at the expense of model fit and predictive performance. This study presents a method for defining MRMs that draws on characteristics of the given benefits transfer scenario and its relationship to the metadata while satisfying the adding up condition. This modelling framework outperforms the model used by EPA in model fit and predictive performance. Applying the results to a recent CWA rule, I find the model used by EPA substantially underestimates the potential benefits.
Essays on Development in Sub-Saharan African Countries
Zhang, Zeya (Virginia Tech, 2021-01-14)
As one of the fastest growing regions in the world, crop production and education remain two of the most important topics for the development of sub-Saharan African (SSA) countries. This dissertation is composed of three chapters that investigate the economic returns to education (Chapter 1 and 2) and assess the policy influence on fertilizer usage (Chapter 3) in two SSA countries, Zimbabwe and Ethiopia. Chapter 1 investigates the casual impact of improved educational attainment on household well-being as reflected by consumption level in Zimbabwe. We use the age-specific exposure to the 1980 education reform as the instrument for the household head educational attainment to identify the economic returns to education. We find that an extra year of household head schooling leads to an 8% increase in per capita household consumption on average when using the multiple rounds of the Income, Consumption and Expenditure Survey (ICES). The impact of enhanced education on household consumption is larger for rural and female-headed households and we also find some evidence that head educational attainment could affect consumption patterns, where additional schooling leads to slightly lower consumption share in food and higher share in non-durable goods. Chapter 2 extends this topic by utilizing a pseudo panel data constructed with multiple waves of repeated cross-sectional data, which allows us to use fixed-effect and other panel data methods to address the problem of unobserved "ability" bias. For pseudo panel, we use age, gender and some other time-persistent criterions to define the cohorts and replace the individual observations with the intra-cohort means. Individual time-invariant factors that influencing both education and consumption are transformed into cohort time-invariant factors, within transformation on the pseudo panel would eliminate such factors leads to achieve unbiased and consistent estimates on the returns to education. We find on average there is a 14% increase in monthly household per capita consumption for each one more year of education for the household head. By further disaggregating our population, we find female-headed households exhibit a return to education of around 15.3%, much higher than its corresponding OLS/IV estimates. On the other hand, we fail to detect such large discrepancy for the male-headed households, suggesting that the overall downward bias of OLS/IV estimates mostly come from female-headed households. Facing significant higher opportunity cost, Zimbabwean females are much less likely to furthering their education when compared to males with similar unobserved ability level which can be one of the major underlying reasons. Chapter 3 investigates the potential effect of fertilizer promotion polices on crop acreage and input intensities in Ethiopia. We use a fully calibrated multi-input and -output model based on the principle of positive mathematical programming (PMP) to assess the policy impact in four major agricultural states in the country. I analyze two policies designed to promote fertilizer use, namely fertilizer import expansion and a universal subsidy program. The results from the simulation model suggest that local farmers actively respond to these promotion policies by adjusting crop acreage and investing more in fertilizer input. However, when the availability of fertilizer in one region is fixed and local farmers face a binding constraint, the behavior responses to the subsidy program alone would be limited.
Essays on the Economics of Climate Change, Water, and Agriculture
Ji, Xinde (Virginia Tech, 2018-08-30)
In an era of global-scale climate change, agricultural production faces a unique challenge due to its reliance on stochastic natural endowments, including temperature, precipitation, and water availability for irrigation. This dissertation presents a series of essays to examine how agricultural producers react and adapt to challenges presented by climate change and scarce irrigation water allocated through the prior appropriation doctrine. The dissertation approaches the problem from three distinct perspectives: institutional differences, climate and water availability, as well as producers' expectation on future endowments. Chapter 2 presents an institutional perspective, in which I investigate how different water allocation mechanisms within the prior appropriation doctrine result in differences in producers' crop allocation decisions. I find that water users in irrigation districts are able to plant more water-intensive crops than farmers outside irrigation districts. Chapter 3 presents the interaction between nature and human systems, in which I examine how the physiological complementarity of temperature and water availability diffuses from crop yield (at the intensive margin) to crop allocation strategies (at the extensive margin). Using a theoretical model I show that the observed complementarity reflects a combination of two mechanisms: yield impact through physiological complementarity, and adaptation response through shifting crop allocation patterns. Using an empirical model, I find that farmers adapt to changing climate conditions by growing more profitable crop mixes when presented with more growing degree-days (GDD), precipitation and groundwater access. Chapter 4 presents a behavioral perspective, in which I test how producers' expectation formation processes lead to short term over-adjustments to weather and water availability fluctuations. Using a fixed-effect regression on lagged weather and water realizations, I find that agricultural producers engage in a combination of cognitive biases, including the availability heuristic and the reinforcement strategy. Adopting these alternative learning mechanisms causes farmers to significantly over-react to more recent fluctuations in weather and water availability when making ex ante acreage and crop allocation decisions.
Essays on the Non-market Valuation and Optimal Control of Bio-invasions in Urban Forest Resources
Siriwardena, Shyamani Dilantha (Virginia Tech, 2017-02-21)
This dissertation consists of three essays, of which, two involve assessing the value of tree cover in urban communities and the other evaluates cooperative management of an invasive species by urban communities. The first chapter summarizes the three topics and briefly describes the motivation, methods applied and main conclusions in each study. Chapter 2 presents a meta-analysis of hedonic property value studies on the value of tree cover. A meta-regression was performed using implicit value estimates for tree cover at property-level from various locations in the U.S. along with auxiliary data of county-level tree cover to investigate the relationship between tree cover and implicit-price estimates for residential properties. The study found that on average 35 percent and 40 percent tree cover respectively at property-level and county-level optimize the benefits to the property owners in urban areas. These results provide insights to forward-looking communities to adapt their tree planting and protection efforts to lessen climate-induced impacts. Chapter 3 applies a first-stage Hedonic property price model to estimate preference for tree cover in urban communities using single-family house sales data from multiple property markets across the U.S. The study analyses how home owners' preference for tree cover vary across the landscape and across cities. Further, it identifies what factors affect these variations via the general inferences obtained from an internal meta-analysis. The study confirms the heterogeneity of preferences as affected by the differences in the abundance of tree cover in study locations, regional differences and household characteristics. These findings add to the hedonic literature and provide useful information for future urban planning. Chapter 4 focuses on cooperative management of invasive species in landscapes with mixed land ownerships. This study analyzes the effect of the land ownership on the management efforts between an infested municipality and an uninfested municipality when a transferable payment scheme is involved in the cooperative agreement. A dynamic optimization problem was set up to evaluate the case of Emerald ash borer (EAB) control in multiple jurisdictions in the Twin Cities, Minnesota. The results suggest that when the infested municipality has more public lands and when the transfer payments are efficiently used to implement greater control, the municipalities are more likely to commit to bargaining, and smaller transfer payments paid over a longer span of time are sufficient for optimal control of the spread of invasive species across the municipalities. The last chapter concludes the three studies and discusses the insights for future research.
Essays on Water Policy and Coupled Human and Natural Systems
Weng, Weizhe (Virginia Tech, 2019-08-02)
Human and freshwater ecosystems are intrinsically interconnected. To better design effective policies, modeling tools and valuation methods are necessary to help understanding the complex reciprocal linkages between ecosystem processes and human actions, and coupled human and natural systems (CNHS) sets up a critical paradigm to do so. It is thus of both academic and empirical appeal to integrate reliable economic valuation methods with tools and models from multiple disciplines in order to quantify the feedbacks between human and natural systems and to inform better policy design. Using freshwater resources as an example, this dissertation contains three essays which integrate natural science and economics models to understand how changes in human behavior and societal policies lead to changes in ecosystem services, and how changes in ecosystem services, in return, affect human decisions. The first two essays focus on agricultural nonpoint source pollution problems in United States and examines the impacts of potential water polices on both water polluters and water demanders. Specifically, in the first essay, a novel coupling between an ecological model of within-lake hydrodynamics and an economic model of hedonic property prices has been developed to quantify the connections between nutrient loading, lake water quality, and economic outcomes. Linking ecological processes with human decision-making provides a basis for enhanced evidence-based decision making in the context of reducing nonpoint-source pollution. In the second essay, an economic mathematical programming model is coupled with an agro-ecosystem model to investigate the behavioral adjustments and environmental pollution outcomes of water quality policies. A complete quantification of costs from all regulating sources are necessary to help pinpoint the efficient water policy design and reflecting the connection between human decisions and ecosystem processes. The third essay focus on the water quantity problem in another developed country, Australia. A discrete choice experiment method has been explored and used to provide estimates of willingness to pay for purchasing irrigation rights to restore a Ramsar-convention wetland. Water policy scenario described in this essay could directly affect the feedback between human and ecosystem processes and serve as a baseline for future planning and policy designs. By offering both conceptual and methodological advancements, this dissertation aims to improve the understanding of coupled human and natural systems and the implementation of water policies. This dissertation also provides a framework to establish multi-disciplinary dialogues and cooperation between scientists and economists in the search of efficient water polices.
Essays on Water Quality Management for the Chesapeake Bay Watershed
Xu, Yuelu (Virginia Tech, 2020-02-19)
Water quality management for agricultural production is a complicated and interesting problem. Hydrological and economic factors must be considered when designing strategies to reduce nutrient runoff from agricultural activities. This dissertation is composed of three chapters that investigate cost-effective ways to mitigate water pollution from agricultural nonpoint pollution sources and explore farmers' incentives when participating in water quality trading programs. Chapter 1 investigates landscape targeting of best management practices (BMPs) based on topographic index (TI) to determine how targeting would affect costs of meeting nitrogen (N) loading goals for Mahantango watershed, Pennsylvania. We use the results from two climate models and the mean of the ensemble of seven climate models to estimate expected climate changes and the Soil and Water Assessment Tool-Variable Source Area (SWAT-VSA) model to predict crop yields and N export. Costs of targeting and uniform placement of BMPs across the entire study area (4.23 km2) are compared under historical and future climate scenarios. We find that with a goal of reducing N loadings by 25%, spatial targeting methods could reduce costs by an average of 30% compared with uniform BMP placement under three historical climate scenarios. Cost savings from targeting are 38% under three future climate scenarios. Chapter 2 scales up the study area to the Susquehanna watershed (71,000 km2). We examine the effects of targeting the required reductions in N runoff within counties, across counties, and both within and across counties for the Susquehanna watershed. We set the required N reduction to 35%. Using the uniform strategy to meet the required N reduction as the baseline, results show that costs of achieving a regional 35% N reduction goal can be reduced by 13%, 31% and 36% with cross-county targeting, within-county targeting and within and across county targeting, respectively. Results from Chapters 1 and 2 suggest that cost effectiveness of government subsidy programs for water quality improvement in agriculture can be increased by targeting them to areas with lower N abatement costs. In addition, targeting benefits are likely to be even larger under climate change. Chapter 3 investigates the landowner's nutrient credit trading behavior when facing the price uncertainty given the credits are allowed to be banked for future use. A two-step decision model is used in this study. For the first step, we determine the landowner's application level of a BMP on working land in the initial time period. The nutrient credits awarded to the landowner depend on the nutrient reduction level at the edge of field generated by the BMP application. For the second step, we use an intertemporal model to examine the landowner's credit trading behavior with stochastic price fluctuations over time and with transaction costs. The theoretical framework is applied with a numerical simulation incorporated with a hydro-economic model and dynamic programming. Nutrient Management (NM) is selected as the BMP on working land to generate N credits. We find that gains to the landowner from credit banking increase with higher price volatility and with higher price drift, but that gains are larger with price volatility. However, for a landowner holding a small amount of nutrient credits, the gains from credit banking are small due to transaction costs.
Examining Implicit Price Variation for Lake Water Quality
Swedberg, Kristen (Virginia Tech, 2020-12-16)
Hedonic models are used to estimate implicit prices for water quality in housing markets. Recent studies aggregate sales across large spatial areas in scaled-up models leading to a concern that these models may overlook regional heterogeneity in water-quality preferences. We estimate scaled-up hedonic models comprised of multiple states and individual states and investigate how observations from subregions can differ. We find that the scaled-up model results are driven by select subregions. The results of this study call into question hedonic models using data for large geographic regions where substantial differences may arise across housing markets.
Forests and fisheries in the Brazilian Amazon: Understanding incentives to comply with conservation efforts
Schons Do Valle, Stella Zucchetti (Virginia Tech, 2017-08-15)
This PhD dissertation represents an effort to understand individual behavior leading to decisions regarding natural resource use and compliance with conservation policy at the government and at the community levels through the analysis of specific cases in the Brazilian Amazon. I first analyze the case of smallholder land clearing along the Transamazon and BR-163 highways in the face of Brazilian Forest Code enforcement by the federal government. My hypothesis is that smallholder land clearing paths over time are affected by assessments of the probability of being caught violating the Forest Code. I develop a dynamic decision model that considers the potential benefits and costs accrued from land clearing through time by a representative smallholder and include her perception of the probability of Forest Code enforcement, unobserved to the researcher. I apply an endogenous switching regressions econometric model to data collected with a sample of 542 households in 2003 and 2013/14. I find that longer land tenure frontiers where there are opportunities for smallholders to transition to cattle grazing from agriculture deserve the attention of enforcement of land clearing laws and restrictions and that the use of the forest by a smallholder is a protective signal that must be considered and encouraged. My results suggest that alleged government efforts to enforce the Forest Code among smallholders in the sample region have been ineffective. The second case I analyze is that of fisher households that enforce community fishing agreements, known as accords, in the floodplains of the Amazon River surrounding the city of Santarém. My hypothesis is that individual households benefit from their own fishing accords enforcement effort through fishing time savings. A factor demand analysis applied to data collected with over 600 households reveals that statistically important drivers of labor demand and fuel include the level of dedication of a household and its history in implementing fishing accords, the landscape, the flood cycle, the distance to the main regional market and biomass. The average household fishing time savings from enforcing accords range between 59 and 36 eight-hour days for a six-month-period, an important argument for continuing the enterprise.
From concept to practice to policy: modeling coupled natural and human systems in lake catchments
Cobourn, Kelly M.; Carey, Cayelan C.; Boyle, Kevin J.; Duffy, Christopher J.; Dugan, Hilary A.; Farrell, Kaitlin J.; Fitchett, Leah Lynn; Hanson, Paul C.; Hart, Julia A.; Henson, Virginia Reilly; Hetherington, Amy L.; Kemanian, Armen R.; Rudstam, Lars G.; Shu, Lele; Soranno, Patricia A.; Sorice, Michael G.; Stachelek, Joseph; Ward, Nicole K.; Weathers, Kathleen C.; Weng, Weizhe; Zhang, Yu (Ecological Society of America, 2018-05-03)
Recent debate over the scope of the U.S. Clean Water Act underscores the need to develop a robust body of scientific work that defines the connectivity between freshwater systems and people. Coupled natural and human systems (CNHS) modeling is one tool that can be used to study the complex, reciprocal linkages between human actions and ecosystem processes. Well‐developed CNHS models exist at a conceptual level, but the mapping of these system representations in practice is limited in capturing these feedbacks. This article presents a paired conceptual–empirical methodology for functionally capturing feedbacks between human and natural systems in freshwater lake catchments, from human actions to the ecosystem and from the ecosystem back to human actions. We address extant challenges in CNHS modeling, which arise from differences in disciplinary approach, model structure, and spatiotemporal resolution, to connect a suite of models. In doing so, we create an integrated, multi‐disciplinary tool that captures diverse processes that operate at multiple scales, including land‐management decision‐making, hydrologic‐solute transport, aquatic nutrient cycling, and civic engagement. In this article, we build on this novel framework to advance cross‐disciplinary dialogue to move CNHS lake‐catchment modeling in a systematic direction and, ultimately, provide a foundation for smart decision‐making and policy.
Granular measures of agricultural land use influence lake nitrogen and phosphorus differently at macroscales
Stachelek, Joseph; Weng, W.; Carey, Cayelan C.; Kemanian, Armen R.; Cobourn, Kelly M.; Wagner, Tyler K.; Weathers, Kathleen C.; Soranno, Patricia A. (2020-12)
Agricultural land use is typically associated with high stream nutrient concentrations and increased nutrient loading to lakes. For lakes, evidence for these associations mostly comes from studies on individual lakes or watersheds that relate concentrations of nitrogen (N) or phosphorus (P) to aggregate measures of agricultural land use, such as the proportion of land used for agriculture in a lake's watershed. However, at macroscales (i.e., in hundreds to thousands of lakes across large spatial extents), there is high variability around such relationships and it is unclear whether considering more granular (or detailed) agricultural data, such as fertilizer application, planting of specific crops, or the extent of near-stream cropping, would improve prediction and inform understanding of lake nutrient drivers. Furthermore, it is unclear whether lake N and P would have different relationships to such measures and whether these relationships would vary by region, since regional variation has been observed in prior studies using aggregate measures of agriculture. To address these knowledge gaps, we examined relationships between granular measures of agricultural activity and lake total phosphorus (TP) and total nitrogen (TN) concentrations in 928 lakes and their watersheds in the Northeastern and Midwest U.S. using a Bayesian hierarchical modeling approach. We found that both lake TN and TP concentrations were related to these measures of agriculture, especially near-stream agriculture. The relationships between measures of agriculture and lake TN concentrations were more regionally variable than those for TP. Conversely, TP concentrations were more strongly related to lake-specific measures like depth and watershed hydrology relative to TN. Our finding that lake TN and TP concentrations have different relationships with granular measures of agricultural activity has implications for the design of effective and efficient policy approaches to maintain and improve water quality.
Groundwater Pumping Decisions and Land Subsidence in the Southern Chesapeake Bay Region of Virginia
Wade, Christopher Michael (Virginia Tech, 2016-07-21)
Land subsidence is the gradual settling or sudden sinking of the earth's surface. According to the United States Geological Survey more than 80% of identified subsidence in the United States is a result of groundwater removal. Due to the hydrologic structure and reliance on the Potomac Aquifer, the Southern Chesapeake Bay region of Virginia has suffered from land subsidence since the 1940s. In coastal regions, land subsidence can increase the risk of flooding. This paper presents a mathematical simulation that predicts land subsidence from groundwater pumping. This simulation is used to see how the location of groundwater pumping, as well as the amount of amount of groundwater pumped would differ from two different groundwater pumping policies. The first policy is aimed at limiting land subsidence in the region, while the second policy aims at limiting the damages from land subsidence. These two policies are used to show that a spatially heterogeneous groundwater pumping policy is necessary to minimize the damages from groundwater pumping when land subsidence is present.
A hydro-economic analysis of end-of-century climate projections on agricultural land and water use, production, and revenues in the U.S. Northern Rockies and Great Plains
Lauffenburger, Zachary H.; Maneta, Marco P.; Cobourn, Kelly M.; Jencso, Kelsey; Chaffin, Brian; Crockett, Anna; Maxwell, Bruce; Kimball, John S. (Elsevier, 2022-08)
Study region,Montana, U.S.A. Study focus Creating adaptation plans for projected imbalances in the western U.S. agricultural water demand-supply system are difficult given uncertainty in climate projections. It is critical to understand the uncertainties and vulnerabilities of the regional agricultural system and hydrologic impacts of climate change adaptation. We applied a stochastic, integrated hydro-economic model that simulates land and water allocations to analyse Montana farmer adaptations to a range of projected climate conditions and the response of the hydrologic system to those adaptations. Satellite observations of crop types, productivity, water use, and land allocation were used for model calibration. A suite of climate models was employed to quantify end-of-century impacts on streamflows, water and land use, production, and net revenues.New hydrological insights for the region Simulations showed summer streamflows were influenced by a state-wide 18.2% increase in agricultural water use. Decreased summer water availability with increased demand could have far reaching impacts downstream. Land use for irrigated crops increased 1.6%, while rainfed crops decreased 6.5%, implying state-level decrease in planted area. Even with increased land and water use for irrigated crops, production decreased 0.5%, while rainfed production decreased 2.7%. Corresponding losses in net revenues totaled 1.5% and 7.2% for irrigated and rainfed crops, respectively.Results highlight vulnerabilities of semi-arid agricultural regions and can aid water managers in sustaining agriculture in these regions.
Identifying Irrigated Areas in the Snake River Plain, Idaho: Evaluating Performance across Composting Algorithms, Spectral Indices, and Sensors
Chance, Eric W.; Cobourn, Kelly M.; Thomas, Valerie A.; Dawson, Blaine C.; Flores, Alejandro N. (MDPI, 2017-06-01)
There are pressing concerns about the interplay between agricultural productivity, water demand, and water availability in semi-arid to arid regions of the world. Currently, irrigated agriculture is the dominant water user in these regions and is estimated to consume approximately 80% of the world’s diverted freshwater resources. We develop an improved irrigated land-use mapping algorithm that uses the seasonal maximum value of a spectral index to distinguish between irrigated and non-irrigated parcels in Idaho’s Snake River Plain. We compare this approach to two alternative algorithms that differentiate between irrigated and non-irrigated parcels using spectral index values at a single date or the area beneath spectral index trajectories for the duration of the agricultural growing season. Using six different pixel and county-scale error metrics, we evaluate the performance of these three algorithms across all possible combinations of two growing seasons (2002 and 2007), two datasets (MODIS and Landsat 5), and three spectral indices, the Normalized Difference Vegetation Index, Enhanced Vegetation Index and Normalized Difference Moisture Index (NDVI, EVI, and NDMI). We demonstrate that, on average, the seasonal-maximum algorithm yields an improvement in classification accuracy over the accepted single-date approach, and that the average improvement under this approach is a 60% reduction in county scale root mean square error (RMSE), and modest improvements of overall accuracy in the pixel scale validation. The greater accuracy of the seasonal-maximum algorithm is primarily due to its ability to correctly classify non-irrigated lands in riparian and developed areas of the study region.

Browsing by Author "Cobourn, Kelly M."

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