Calvin Wolter - Academia.edu (original) (raw)

Papers by Calvin Wolter

2016 10th International Drainage Symposium, 2016

Abstract. Drainage density has long been considered a fundamental watershed property to describe ... more Abstract. Drainage density has long been considered a fundamental watershed property to describe how well or how poorly a watershed is drained by stream channels. But where do stream channels begin in watersheds that have been hydrologically altered and drained by extensive subsurface tile networks? In this presentation, the evolution of drainage density in two small Iowa watersheds from pre-settlement times to current conditions is discussed. One watershed (Bear Creek) is located in the recently glaciated Des Moines Lobe (DML) region where tile drainage is widespread and intense. In contrast, the Walnut Creek watershed is located in an older glacial landform region (Southern Iowa Drift Plain, SIDP) where tile drainage is concentrated in swales and grass waterways. While the number of streams per watershed area and total stream length is greater in older landscapes (SIDP) compared to younger landscapes (DML), in all regions, drainage density increases with expansion of tile drainage. In Bear Creek, drainage density increased from 0.0006 m-1 based on the currently delineated perennial stream network to 0.04 m-1 if drainage density from tiles is considered. Increasing drainage density reduces groundwater travel times and decreases opportunities for landscape-scale nutrient processing. Tile drainage reduced average groundwater travel times by 50% in Walnut Creek, and in Bear Creek, average groundwater travel times were reduced from approximately 80 years to 1 year with increasing tile drainage density. With expansion of tile drainage networks in many Midwestern agricultural watersheds, the natural evolution of stream channel has been bypassed and the traditional concept of drainage density does not apply. Does drainage density apply to only mappable surface stream systems or should it include the interconnected subsurface drainage network? It is clear that tile drainage is a fundamental watershed property of many agricultural landscapes and efforts should be directed at better characterizing its spatial extent and capacity to assess the contribution of tile drainage to watershed export.

Journal of Soil and Water Conservation, 2010

Cold-water streams have been a key water resource in northeast Iowa since the settlement of the s... more Cold-water streams have been a key water resource in northeast Iowa since the settlement of the state and support a variety of recreational opportunities, including trout fisheries. According to Kalishek (2005), it is not clear which Iowa streams sustained trout prior to European settlement. However, Kalishek notes comments recorded by biologist Seth Meek, indicating that trout

Eye tracking is the process of recording a person's eye movement for the better understanding of ... more Eye tracking is the process of recording a person's eye movement for the better understanding of his/her visual perception. Due to low costs and highly accurate systems the process of eye tracking is used in devices and applications to increase computer interaction and to study human behavior. Eye tracking is used in a wide range of applications but is almost absent in the engineering domain (e.g., production processes). The cause could be that engineering is an exact science and product design is based on a rigorous set of physical, functional and legal constraints. This study deals with the usage of the Eye tracking technique in the automotive environment. Particularly, it will be used to optimize the quality assurance of paint and the manufacturing of head-up displays in automotive manufacturing. The objective of the studies is to examine the quality assurance cycles regarding optimized working conditions and improved production quality.

American Journal of Agricultural Economics, 2016

On October 12-13, a workshop funded by the National Science Foundation was held at Iowa State Uni... more On October 12-13, a workshop funded by the National Science Foundation was held at Iowa State University in Ames, Iowa with a goal of identifying research needs related to coupled economic and biophysical models within the FEW system. Approximately 80 people attended the workshop with about half representing the social sciences (primarily economics) and the rest from the physical and natural sciences. The focus and attendees were chosen so that findings would be particularly relevant to SBE research needs while taking into account the critical connectivity needed between social sciences and other disciplines. We have identified several major gaps in existing scientific knowledge that present substantial impediments to understanding the FEW system. We especially recommend research in these areas as a priority for future funding: 1. Economic models of decision-making in coupled systems Deliberate human activity has been the dominant factor driving environmental and land-use changes fo...

Journal of Hydrology, 2021

Abstract Although diffuse groundwater recharge is difficult to quantify at a regional scale, base... more Abstract Although diffuse groundwater recharge is difficult to quantify at a regional scale, baseflow discharge can be used in watersheds with gaining streams with negligible effects from pumping. In Iowa, where these conditions are met, we investigated how watershed-scale baseflow calculated from a network of 132 streamflow gages can be used to quantify spatial and temporal patterns of groundwater recharge across a region; and characterize the emergence and expansion of drought conditions in the state. Mean annual groundwater recharge for the 2000–2017 study period estimated by area-weighting annual baseflow was found to be approximately 220 mm but vary widely from 73 to 467 mm based on precipitation inputs. Recharge was found to be particularly concentrated in the months of March to July which accounted for 66% of the average annual recharge. Baseflow discharged from the drought-impacted headwater basins was highly correlated to U.S. Drought Monitor designations in Iowa headwater basins and thresholds varied among landscape regions due to differences in soils and hydrology. Economic losses due to drought were found to substantially increase when annual groundwater recharge was less than approximately 130 mm yr−1. Overall, study results suggest that regional groundwater recharge and drought susceptibility can be reliably assessed using baseflow available from networked stream gages.

Journal of Soil and Water Conservation, 2016

Previous research predicted that the biofuel-driven expansion of corn (Zea mays L.) area would in... more Previous research predicted that the biofuel-driven expansion of corn (Zea mays L.) area would increase riverine export of nitrate-nitrogen (NO 3-N) in the Mississippi River Basin. Accurate information about water quality trends in agricultural watersheds is needed to better inform agricultural policy and to help quantify the effectiveness of field and landscape management practices. This study was designed to (1) characterize possible NO 3-N trends within the Raccoon River watershed (RRWS) of central Iowa, and (2) explore links between the relative areas planted to corn and soybean (Glycine max) and water quality. We examined NO 3-N concentration and loading data from more than 60 main stem river and tributary locations in the RRWS for the period 1999 to 2014. In addition, we assessed the role of climate, crop rotations, and simplified annual N budgets on NO 3-N concentrations and loads to show that expansion of corn area has not increased Raccoon River NO 3-N levels. Nitrate-N concentrations have not increased as corn area increased 19% and fertilizer N inputs increased 24% since 1999. We conclude that expansion of corn area at the expense of soybean may be affecting water quality. Better management of soybean in a corn-soybean rotation should reduce NO 3-N export from the watershed, and reducing throughput of water in this artificially drained system will improve water quality.

Journal of Visualized Experiments, 2012

Water Works is a public water supply serving Des Moines metropolitan area of 400,000 people DMWW ... more Water Works is a public water supply serving Des Moines metropolitan area of 400,000 people DMWW source water includes surface water collected directly from the Raccoon and Des Moines Rivers Water sources are designated as Class "C" as a raw water source of potable water supply so drinking water standards are applicable The applicable water quality standard for nitrate for Class "C" designated use is the USEPA maximum contaminant level (MCL) of 10 mg/l.

Journal of Soils and Sediments

PurposeSoil erosion is an ongoing global agricultural crisis. Quantifying and tracking soil erosi... more PurposeSoil erosion is an ongoing global agricultural crisis. Quantifying and tracking soil erosion and sediment export from agricultural watersheds is a key component for evaluating long-term sustainability.Materials and methodsOur study used Revised Universal Soil Loss Equation soil erosion estimates and concentration of total suspended solids in-stream (determined through relationships with in-stream turbidity measurements) to estimate sediment delivery to an Eastern Iowa stream from a 780-ha watershed in 2015. Furthermore, we quantified soil organic carbon (SOC) and nitrogen (N) storage within the plow layer of our study area and used our estimated soil loss values to determine particulate nutrient export to the stream. These values were compared to in-stream nutrient sensor data in order to quantify the proportion of N in-stream coming from soil erosion compared to other sources.Results and discussionResults indicate that soil erosion in 2015 was approximately 7.5 Mg ha−1. Sediment export to the stream was determined to be 279 kg ha−1 and the sediment delivery ratio was estimated to be 3.7%. SOC and N stocks were 40 and 2.5 Mg ha−1, respectively. Approximately 0.01% of total SOC and N were lost from the plow layer in 2015.ConclusionsThis study identifies long-term risks to watershed sustainability and water quality associated with soil erosion which directs watershed managers towards Best Management Practices that may more effectively reduce export of soil and nutrients while increasing the sustainability of an essential agricultural industry.

Landscape Ecology

ContextRiparian buffers reduce subsurface nutrient losses to streams but there is a clear need to... more ContextRiparian buffers reduce subsurface nutrient losses to streams but there is a clear need to identify and prioritize locations for riparian buffer placement to optimize buffer performance. Scaling relations can be used to extrapolate hydrologic behavior within river networks and across catchments.ObjectivesWe combined field and laboratory measurements of soils and groundwater quality collected at five riparian monitoring sites of different stream-order scales with landscape analysis to accomplish the following objectives: (1) evaluate the degree to which riparian zone patterns and processes are scaled in a pre-Wisconsin glacial landscape; and (2) use the scaling information to identify optimal placement of riparian buffers in the landform region for nutrient reduction benefits.ResultsResults indicated that there is proportional scaling of riparian zones within the region in terms of sediment texture, groundwater geochemistry and, to a lesser extent, in groundwater nutrient concentrations.ConclusionsPlacement of riparian buffers should be a priority along low order streams (< 3rd order) to best utilize the scaling characteristics of regional riparian zones, although buffering 2nd and 3rd streams may be the most cost effective locations.

38th IAHR World Congress - "Water: Connecting the World"

Science of The Total Environment

Floodplain storage commonly represents one of the largest sediment fluxes within sediment budgets... more Floodplain storage commonly represents one of the largest sediment fluxes within sediment budgets. In watersheds responding to large scale disturbance, floodplain-channel lateral connectivity may change over time with progression of channel evolution and associated changes in channel geometry. In this study we investigated the effects of channel geometry change on floodplain inundation frequency and flux of suspended sediment (SS) and total phosphorus (TP) to floodplain storage within the 52.2 km2 Walnut Creek watershed (Iowa, USA) through a combination of 25 in-field channel cross section transects, hydraulic modeling (HEC-RAS), and stream gauging station-derived water quality and quantity data. Cross sectional area of the 25 in-field channel cross sections increased by a mean of 17% over the 16 year study period (1998-2014), and field data indicate a general trend of degradation and widening to be present along Walnut Creek's main stem. Estimated stream discharge required to generate lateral overbank flow increased 15%, and floodplain inundation volume decreased by 37% over study duration. Estimated annual fluxes of SS and TP to floodplain storage decreased by 61 and 62% over study duration, respectively. The estimated reductions in flux to floodplain storage have potential to increase watershed export of SS and TP by 9 and 18%, respectively. Increased contributions to SS and TP export may continue as channel evolution progresses and floodplain storage opportunities continue to decline. In addition to loss of storage, higher discharges confined to the channel may have greater stream power, resulting in further enhancement of SS and TP export through accelerated bed and bank erosion. These increased contributions to watershed loads may mask SS and TP reductions achieved through edge of field practices, thus making it critical that stage and progression of channel evolution be taken into consideration when addressing sediment and phosphorus loading at the watershed scale.

Ambio

Growth and consolidation in the livestock industry in the past 30 years have resulted in more tot... more Growth and consolidation in the livestock industry in the past 30 years have resulted in more total farm animals being raised on fewer Iowa farms. The effects of this on stream water quality at the landscape scale have largely gone unexplored. The main objective of this work was to quantify the effects on stream nitrate levels of livestock concentration in two western Iowa watersheds relative to seven other nearby watersheds. To achieve this objective, we used data on high-frequency nitrate concentration and stream discharge, commercial nitrogen fertilizer use, and manure-generated nitrogen in each watershed. Our analysis shows much higher stream nitrate in the two watersheds where livestock concentration has been greatest, and little difference in commercial fertilizer inputs with the widespread availability of manure N. Reducing N inputs and better management of manure N, including analysis of crop N availability in soil and manure, can reduce uncertainty regarding fertilization while improving water quality.

JAWRA Journal of the American Water Resources Association

Several biofuel cropping scenarios were evaluated with an improved version of Soil and Water Asse... more Several biofuel cropping scenarios were evaluated with an improved version of Soil and Water Assessment Tool (SWAT) as part of the CenUSA Bioenergy consortium for the Boone River Watershed (BRW), which drains about 2,370 km2 in north central Iowa. The adoption of corn stover removal, switchgrass, and/or Miscanthus biofuel cropping systems was simulated to assess the impact of cellulosic biofuel production on pollutant losses. The stover removal results indicate removal of 20 or 50% of corn stover in the BRW would have negligible effects on streamflow and relatively minor or negligible effects on sediment and nutrient losses, even on higher sloped cropland. Complete cropland conversion into switchgrass or Miscanthus, resulted in reductions of streamflow, sediment, nitrate, and other pollutants ranging between 23-99%. The predicted nitrate reductions due to Miscanthus adoption were over two times greater compared to switchgrass, with the largest impacts occurring for tile-drained cropland. Targeting of switchgrass or Miscanthus on cropland ≥2% slope or ≥7% slope revealed a disproportionate amount of sediment and sediment-bound nutrient reductions could be obtained by protecting these relatively small areas of higher sloped cropland. Overall, the results indicate that all biofuel cropping systems could be effectively implemented in the BRW, with the most robust approach being corn stover removal adopted on tile-drained cropland in combination with a perennial biofuel crop on higher sloped landscapes.

Environmental Monitoring and Assessment

Journal of Soil and Water Conservation

Screenshot of map of the Mississippi River Basin, showing portions of the states of Illinois, Iow... more Screenshot of map of the Mississippi River Basin, showing portions of the states of Illinois, Iowa, and Wisconsin. Blue lines correspond to the boundaries of hydrologic unit code (HUC)-12 watersheds. The fill color inside each HUC-12 corresponds to the ranking of the watershed in terms of nitrogen (N) export to the Gulf of Mexico, with warmer colors corresponding to higher rankings. The user can zoom into individual HUC-12 watersheds to get more information.

Journal of environmental quality, 2017

Phosphorus (P) is delivered to streams as episodic particulate P and more continuous soluble P (o... more Phosphorus (P) is delivered to streams as episodic particulate P and more continuous soluble P (orthophosphorus [OP]), and it is important to determine the proportion of each P form in river water to more effectively design remedial measures. In this study, we evaluated the annual mean ratios of OP to total P (TP) concentrations and loads in 12 Iowa rivers and found systematic variation in the ratios. The OP/TP ratios were >60% in two tile-drained watersheds of the Des Moines Lobe and in a shallow fractured bedrock watershed in northeast Iowa, whereas in southern and western Iowa, OP contributions to TP were <30%. Higher OP/TP ratios were associated with greater row crop intensity in the watershed and a greater proportion of baseflow in the river. Orthophosphorus contributions from croplands would be greater in watersheds characterized by widespread tile drainage and well-drained soils, whereas cropland TP export would be dominated by particulate P in dissected till plains wit...