2021 Abstracts

2021 WESTERN SOUTH DAKOTA HYDROLOGY CONFERENCE

Program and Abstracts

April 21–22, 2021 Virtual conference

2021 Western South Dakota Hydrology Conference

This program and abstracts book has been produced in conjunction with the virtual 2021 Western South Dakota Hydrology Conference (19th annual). This document provides summaries of the presentations made during the conference, and gives attendees contact information for the presenters for additional questions or collaboration following the conference.

The purpose of the Western South Dakota Hydrology Conference is to bring together researchers from Federal, State, University, local government, and private organizations and provide a forum to discuss topics dealing with water, energy, and environmental issues in western South Dakota and the entire upper Great Plains region. This meeting provides an opportunity for hydrologists, geologists, engineers, scientists, geographers, students, and other interested individuals to exchange ideas, discuss mutual problems, and summarize results of studies.

ACKNOWLEDGMENTS

Many people have contributed to this meeting. The presenters are thanked for their contributions and moderators are thanked for their help in streamlining the presentations. The organizing agencies are thanked for support: National Weather Service, RESPEC, South Dakota Department of Agriculture and Natural Resources, South Dakota School of Mines and Technology, U.S. Geological Survey, and West Dakota Water Development District. The chairpersons for this meeting were Melissa Smith (National Weather Service), Lacy Pomarleau (RESPEC), Joanne Noyes (South Dakota Department of Agriculture and Natural Resources), Scott Kenner (South Dakota School of Mines and Technology), Liangping Li (South Dakota School of Mines and Technology), J. Foster Sawyer (South Dakota School of Mines and Technology), Arden Davis (South Dakota School of Mines and Technology), Galen Hoogestraat (U.S. Geological Survey), Dan Driscoll (West Dakota Water Development District), and Mark Anderson (U.S. Geological Survey / South Dakota School of Mines and Technology). The West Dakota Water Development District and RESPEC are thanked for being executive sponsors of this conference. Thanks also to sponsors: Citizens' Climate Education, Banner Associates Inc., Black Hills Clean Water Alliance, HDR Engineering Inc., and LRE Water.

2 Promoting sustainability through innovative solutions

Featuring world-class scientific and academic leadership, RESPEC is the premier provider of water, environmental, and natural resources engineering and technology in North America. We help clients adapt to the dynamically changing present and prepare for water demands of the future. 2021 WESTERN SOUTH DAKOTA HYDROLOGY CONFERENCE PROGRAM

Session 1 – 8:00 – 10:00 AM, Wednesday 4/21/2021

Galen Hoogestraat and Mark Anderson, 8:00 – 8:10 AM Welcome and announcements USGS Brian Walsh, Public Affairs Director, SD 8:10 – 8:30 AM SD Department of Agriculture / DENR Merger Update DANR Overview of West Dakota Water Development District stormwater Dan Driscoll, West Dakota Water 8:30 – 8:50 AM inventory and erosion control projects Development District Pilot Project for an Inventory of Impervious Areas and Green Spaces 8:50 – 9:10 AM Jason Phillips, SDSMT and TerraSite Design that may have Potential for Future Stormwater Mitigation Measures Hydrogeology and Dewatering Scenarios for Summerset, South 9:10 – 9:30 AM Bill Eldridge and Todd Anderson, USGS Dakota Improving the City of Spearfish’s FEMA Floodplain Mapping with 2D 9:30 – 9:50 AM Amber Lefers, AE2S Hydraulic Modeling 9:50 – 10:00 AM BREAK – Sponsor recognition

Session 2 – 10:00 AM – 12:00 PM, Wednesday 4/21/2021 Jon Zufelt and Dennis Reep, HDR 10:00 – 10:30 AM Ice-affected flow analyses in the Lower Heart River Levee System Engineering Water-Quality Assessment of the Heart River Basin, North Dakota, 10:30 – 10:50 AM Wyatt Tatge, USGS 1970-2019 The LaPrele Dam Project, Douglas, WY: Project History, Investigation Peter Rausch, RESPEC, and Cory Foreman, 10:50 – 11:20 AM and Design Options HDR Engineering An update of surface and subsurface geological mapping, Mike Wiles, Erin Dundas, and Sierra Heimel 11:20 – 11:40 AM potentiometric map, and flow directions in the Madison aquifer Jewel Cave National Monument at Jewel Cave National Monument Modeling transport and retention of graphene oxide in biochar media Md Sazadul Hasan, Venkataramana 11:40 – 12:00 PM under subsurface aquatic environment Gadhamshetty, and Mengistu Geza, SDSMT

Session 3 – 8:00 – 10:00 AM, Thursday 4/22/2021

8:00 – 8:05 AM Welcome and announcements Lacy Pomarleau, RESPEC Tim Cowman Impacts of Sedimentation on Missouri River Reservoirs and Free- 8:05 – 8:30 AM South Dakota DANR; Geological Survey Flowing Segments Program Analysis of Potential Alternative Operations for Pactola and Deerfield David Waterman and Rosemary Squillace, 8:30 – 8:50 AM Reservoirs SDSMT Hydraulic Analysis of Fish Habitat Restoration of Rapid Creek Anne Winckel, SDSMT and RESPEC, and 8:50 – 9:10 AM Downstream of Pactola Reservoir Scott Kenner, SDSMT Examining the Influence of Climate Change on Stream Yield in the Lucas Graunke, Lisa Kunza, William 9:10 – 9:30 AM Black Hills of South Dakota Capehart, and Mengistu Nisrani, SDSMT Characterization of Factors Affecting Groundwater Levels in and near 9:30 – 9:50 AM the Rosebud Indian Reservation and the Former Lake Traverse Indian Kristen Valseth, USGS Reservation, 1956-2017 9:50 – 10:00 AM BREAK – Sponsor recognition

Session 4 – 10:00 AM – 12:00 PM, Thursday 4/22/2021

Mesonet Monitoring of Soil Moisture and Snowpack Monitoring in the Nathan Edwards, South Dakota State 10:00 – 10:20 AM Upper Missouri River Basin University – South Dakota Mesonet

10:20 – 10:50 AM From the Ground Up - Managing Water for Quality and Quantity John McMaine, South Dakota State University

Fleford Redoloza, Tanja Williamson, and 10:50 – 11:10 AM Image Segmentation of Tile Drainage Systems Using U-Nets Alex Headman, USGS Investigation of Muskingum Routing parameters in natural channel in Vida Atashi and Yeo Lim, University of North 11:10 – 11:30 AM North Dakotan river under snowmelt-induced flooding conditions Dakota

11:30 – 12:00 PM Improving Water quality with the Scenario Application Manager (SAM) Seth Kenner, RESPEC

WEDNESDAY, APRIL 21, 2021 SESSION 1 8:00 – 10:00 A.M.

SD DEPARTMENT OF AGRICULTURE / DENR MERGER UPDATE

Brian Walsh Public Affairs Director, SD Department of Agriculture and Natural Resources [email protected]

OVERVIEW OF WEST DAKOTA WATER DEVELOPMENT DISTRICT "STORMWATER-INVENTORY" AND "EROSION-CONTROL" PROJECTS

Dan Driscoll Area 3 Director, West Dakota Water Development District [email protected]

During 2020 the West Dakota Water Development District implemented two projects that aim to improve water-quality and ecological conditions in Rapid Creek. Rapid Creek often fails to meet designated water-quality standards for total suspended solids during periods of urban stormwater runoff, which is widely recognized as a common cause for exceedance of water-quality standards.

Both projects were implemented as partnerships with the Civil and Environmental Engineering Department at South Dakota Mines. The stormwater-inventory project, which has essentially been completed, was implemented as a pilot-level effort within 3 of Rapid City’s 27 named urban drainage basins. The primary goal was to develop methods for identifying non-residential properties where future improvements in stormwater management might be accomplished with minimal effort and cost. Such properties typically were developed before the advent of modern stormwater best management practices. Good candidates for future improvements might include properties with relatively large impervious surfaces and available green space well suited for stormwater mitigation.

The erosion-control project also was implemented as a pilot-level effort and has a purpose of testing methods for slope stabilization through revegetation in challenging settings where highly erosive soils are present. The end goal is to achieve water-quality improvement by reducing erosion and associated sedimentation within the downstream receiving water body. The project area consists of about 2 acres of exposed weathered shale on a steep slope on the west side of the South Dakota Mines campus. Many other large areas with actively eroding shales exist within the South Dakota Mines campus and on slopes surrounding the “Star Village” and “Hillcrest” housing units to the west, where future erosion-control projects might be considered.

PILOT PROJECT FOR AN INVENTORY OF IMPERVIOUS AREAS AND GREEN SPACES THAT MAY HAVE POTENTIAL FOR FUTURE STORMWATER MITIGATION MEASURES

Jason Phillips South Dakota Mines and TerraSite Design [email protected] [email protected]

Urban stormwater runoff is a detrimental factor to the water quality and ecology of Rapid Creek within the urban/suburban corridor. It also contributes to increased flash flooding because existing infrastructure can’t handle the increased runoff generated from the increased impervious land cover. The use of modern stormwater best management practices (BMPs), that incorporate green infrastructure (GI), can be quite effective in mitigating detrimental effects of stormwater runoff; however, much of Rapid City’s urbanization occurred before the advent of effective stormwater BMPs. A comprehensive large scale program to “retrofit” all areas within the Rapid City vicinity lacking adequate stormwater infrastructure would be a costly and long-term process. However, adding small scale GI retrofits that promote on-site stormwater management would be steps in the right direction.

The purpose of this project was to implement a pilot-level effort to work within 3 of Rapid City’s 27 named urban drainage basins to develop approaches for (1) inventorying green spaces and impervious surfaces, focusing primarily on directly connected impervious areas (DCIA) and (2) develop a series of inventory parameters (fields) that could be used for ranking and prioritizing areas for future GI retrofits with minimal cost. GIS was used to develop a geodatabase/prioritization tool for ranking and prioritizing each site. There were 360 sites inventoried throughout the three drainage basins. Meade Hawthorne had 115 sites, Race Track had 51 sites, and Knollwood had 194 sites. Each site was ranked on a scale of 1 to 5, 5 having the highest potential for implementing a stormwater project with the best benefit/cost ratio. Meade Hawthorne had 36 sites, Racetrack had 6, and Knollwood had 28 sites with the highest potential for GI implementation projects. Overall, this project was a success. The prioritization tool and the data collected using it will be valuable for planning future stormwater projects.

HYDROGEOLOGY AND DEWATERING SCENARIOS FOR SUMMERSET, SOUTH DAKOTA

William G. Eldridge and Todd M. Anderson U.S. Geological Survey: Dakota Water Science Center [email protected] [email protected]

The city of Summerset is a growing community in western South Dakota. The Sun Valley Estates subdivision in the northern part of Summerset was developed on unconsolidated alluvial deposits surrounded by steep terrain. Groundwater levels in the deposits increase during years with greater than normal precipitation. In 2019, increasing groundwater levels caused damage to stormwater systems, to sewer infrastructure, and to houses with basements. The U.S. Geological Survey, in cooperation with the city of Summerset and the South Dakota School of Mines and Technology, completed a study of the hydrogeology and groundwater flow in the unconsolidated alluvial deposits in northern Summerset. The purpose of the study was to 1) characterize the groundwater system in the area, 2) provide hydrogeologic information in support of future development and planning, and 3) simulate the efficiency of pumping for dewatering areas near houses prone to basement flooding.

IMPROVING THE CITY OF SPEARFISH’S FEMA FLOODPLAIN MAPPING WITH 2D HYDRAULIC MODELING

Amber Lefers Advanced Engineering and Environmental Services, Inc. (AE2S) [email protected]

Spearfish Creek is a highly valuable trout stream flowing through the City of Spearfish, SD. Once the creek enters the City, severe floods can cause flood flows to break away from the main channel and travel in separate flow paths. However, portions of the FEMA floodplain maps do not accurately account for these break away flows. Because of the complex flow routes for the break away flows, a combined 1D-2D model was built for the entire Spearfish Creek channel and floodplain from the canyon to the north end of the City. This complex analysis was a unique floodplain submittal for FEMA, which required several innovative approaches to meet FEMA mapping standards while at the same time accurately illustrating the flood risk for the community.

These unique approaches included: • Mapping all the break-away flows using the 2D portion of the model; • Mapping the main channel floodplain and floodway assuming all the flood flows remain along the channel and adjacent overbanks in case debris or other obstructions block the break-away flows; • Mapping an extensive shallow-flooding area with a rarely-used FEMA flood zone to streamline floodplain administration; and • Revising flood elevations along nearly 5 miles of Spearfish Creek, flood elevations along 5 different break-away flow routes totaling over 3.5 of additional miles. • Using up-to-date hydrology for Spearfish Creek to provide the best estimate of flood peaks

WEDNESDAY, APRIL 21, 2021 SESSION 2 10:00 A.M. – 12:00 P.M.

ICE-AFFECTED FLOW ANALYSES IN THE LOWER HEART RIVER LEVEE SYSTEM

Jon Zufelt and Dennis Reep HDR Engineering, Inc. [email protected] [email protected]

The Lower Heart River Levee System, located at Mandan, North Dakota, was constructed by the USACE in the 1940s and 1950s and protects significant portions of the community from Heart River flooding just above its confluence with the Missouri River. The drainage area to the Heart River is 3,310 square miles at the gage at Mandan (USGS 06349000), with two USBR dams (Dickinson Dam and Heart Butte Dam) upstream which control approximately 1,800 square miles. Three main segments make up the 11.77 miles of levee system: Sunny Unit (3.96 miles); North Unit, also known as the Mandan Unit, (4.23 miles of levee and 0.08 miles of floodwall); and the Lower Unit (3.49 miles). The system sponsor is the Lower Heart River Water Resource District (WRD).

Ice jams and ice affected flow have plagued the system throughout its history, and a 2012 FEMA hydrologic and hydraulic study as part of the levee recertification effort identified significant freeboard deficiencies throughout the system based on concurrent ice jamming and free flow 100-year discharges. Based on those findings, a significant rehabilitation was planned to bring the levee system up to FEMA standards with an estimated project cost of $36 million for the North and Lower Units which provide most of the protection to the community.

In 2018, the WRD pursued a revised hydrologic and hydraulic analysis which focused on the impossibility of concurrent 100-year free flow discharges and ice jamming events. As a result of that revised approach, a majority of the freeboard deficiencies were eliminated, and the cost of the recertification rehabilitation efforts significantly reduced.

The presentation will focus on the ice-affected flow analyses as it relates to FEMA regulatory base flood elevations.

WATER-QUALITY ASSESSMENT OF THE HEART RIVER BASIN, NORTH DAKOTA, 1970-2019

Wyatt Tatge U.S. Geological Survey: Dakota Water Science Center [email protected]

Dissolved ion concentrations have been increasing in streams within the Heart River Basin in west-central North Dakota. A concern to agricultural producers is soil salinity and the quality of irrigation water, both of which are directly tied to the increasing dissolved ion concentrations in the Heart River and its tributaries. To better understand the water-quality of the Heart River Basin, water-quality trends were computed for historical (1974-2019) and recent (1999-2019) periods at five stream sites to determine changes over time. Geochemical modeling was done at select stream sites to determine the source of chemistry changes in the channel. R-QWTREND was used to characterize dissolved ion concentration trends to determine changes from factors other than streamflow. PHREEQC inverse modeling was used to better understand the geochemical reactions controlling water-quality within the Basin. Results of the trend analysis indicated that sulfate, sodium, calcium, potassium, magnesium, chloride, and total dissolved solids had increasing trends in both the historical or recent trend periods. Results of the geochemical modeling indicated that increased dissolved ion concentrations were derived mainly from sulfate evaporites that include gypsum, konyaite, mirabilite, and thenardite that are in the soils and geology of the Heart River Basin. Characterization of these results will better assist producers and water-resource managers in making informed decisions regarding best management practices to protect soil health and the quality of irrigation water.

THE LAPRELE DAM PROJECT, DOUGLAS, WY

Peter Rausch RESPEC [email protected]

Cory Foreman HDR [email protected]

The LaPrele Dam is owned and operated by the LaPrele Irrigation District (LID) and is located on LaPrele Creek, a tributary to the North Platte River, approximately 15 miles west of Douglas, Wyoming in Converse County. The dam provides 20,000 acre-feet of storage for104 water users irrigating 11,462 acres of mainly alfalfa.

PART 1: PROJECT HISTORY The LaPrele Dam was constructed in 1909 and stands135 feet high with a 320-foot long crest. The dam consists of a reinforced, concrete slab sloping upward at 40 degrees from horizontal supported by buttresses, known as a slab-and-buttress, or Ambursen style. Due to its height, capacity, and potential threat to life and infrastructure downstream (including Interstate 25), the LaPrele Dam has a High Hazard rating. In 1965 and 1970, heavy snowmelt combined with spring storms to fill the reservoir to the dam’s parapet, resulting in large spillway outflows and raising concerns about the dam’s stability and safety. These flooding events, along with seepage, sliding, spillway, and face slab issues, prompted a rehabilitation of the dam that was completed in1979 through private investment.

In 2017 and 2018, the Wyoming Water Development Commission (WWDC) funded a study to inventory and assess the LaPrele Irrigation District systems. That study led to further, preliminary investigation of the dam in September 2019 which identified multiple cracks and deterioration of concrete in features at the west end of the dam. As a result, the Wyoming State Engineer’s Office issued a restriction on the LaPrele Reservoir, limiting storage to about 55 percent of capacity on November 20, 2019. This was followed up by a thorough investigation of the entire dam in December of 2019. This investigation identified widespread shear cracking in the buttresses and poor concrete strengths throughout, which led to the recommendation to investigate options for replacement or major repair.

PART 2: INVESTIGATION & DESIGN OPTIONS In 2020, the WWDC funded a second project phase to evaluate options for addressing the issues with LaPrele Dam. This included preliminary geotechnical investigations and foundational geology assessment at the dam site, further assessment of the existing structure, and assessment of the LaPrele Creek Watershed hydrology. With this information, design options were developed, assessed, and ranked. The options evaluated include a major infill/repair of the existing dam or replacement with either a roller- compacted concrete (RCC) dam, a concrete arch dam, a rockfill dam, or an earthfill dam.

The LaPrele Irrigation District is working with the WWDC to identify funding opportunities to further investigate options for replacement or major infill/ repair of the LaPrele Dam.

AN UPDATE OF SURFACE AND SUBSURFACE GEOLOGICAL MAPPING, POTENTIOMETRIC MAP, AND FLOW DIRECTIONS IN THE MADISON AQUIFER AT JEWEL CAVE NATIONAL MONUMENT

Mike Wiles, Erin Dundas, and Sierra Heimel Jewel Cave National Monument [email protected] [email protected] [email protected]

Jewel Cave has over 208 miles (335 km) of mapped passages, representing only three percent of the entire cave system. This work seeks to establish clear relationships between surface and subsurface geological features, that will eventually help predict the location of unknown cave passages based on the surface geology. The Jewel Cave fault zone has been mapped many times since the 1920s. No two versions are alike. They range from overly simplified to overly complex, with seemingly random structural features. Using subtle distinctions between Minnelusa subunits, this work demonstrates that the fault zone consists of linear features, beginning with a few high displacement faults at its east end, totaling 600 feet. To the west, it progressively splinters into subordinate faults, each accounting for a smaller amount of displacement. Only these minor faults cross Hell Canyon, before disappearing on the west side. Most of the known cave passages are within the southernmost block, and show only minor internal structural deformation. However, the block itself is separated from the rest of the limestone by a fault with 100 feet of displacement. Calcite spar within vugs of the northern upthrown block suggest that this occurred after the cave stopped forming, within the last 14.7 million years. It’s difficult to map structures within the cave because there are few planar surfaces, most of which are out of reach. However, Dundas created a spreadsheet to solve the “3-point problem” and calculate the strike and dip of an unreachable surface by using a laser survey tool to take three survey shots from a common reference point. This allows a degree of accuracy far exceeding what can be obtained on the surface. Although actual prediction of undiscovered cave passages remains a long way off, these efforts provide a more reliable geological framework for pursuing that ultimate goal.

Since 2015, cave explorers have discovered several cave lakes, at locations where cave passages intercept the Madison aquifer. The lakes provides direct access to the aquifer, and an opportunity to update a map of its potentiometric surface and determine the groundwater flow directions through the Jewel Cave area. Improved understanding of groundwater levels and flow within the Madison aquifer allows scientists, park managers, and the surrounding communities to better manage, protect, and preserve the aquifer, as well as the cave and its unique natural features.

The updated potentiometric-surface map covers an area of about 1,000 square miles (259 x 103 hectares) surrounding Jewel Cave. It was constructed using water levels measured from calendar years 1998 to 2019 in 24 groundwater wells and four cave lakes. Hydrographs were constructed using continuous water levels from four observation wells and one cave lake (Hourglass Lake), and discrete measurements at three other cave lakes, to evaluate historical and current groundwater recharge to the Madison aquifer in the study area. Hydrographs from 1992 through 2018 indicated water levels were lowest from the early to mid-1990s, increased through the late 1990s, peaked in the early 2000s, decreased until 2010, and then increased to the highest levels during 2016–18.

The final map indicates that groundwater near Jewel Cave originates from recharge to the Madison aquifer in the higher elevations in the north-central area of the map, flows west to south-southwest through the Jewel Cave area, and then southeast. In some cases, potentiometric contours pass through unsaturated zones of the Madison Limestone because of interpolation or data gaps. Future modeling can be refined to exclude areas with known dry well holes and canyons that penetrate the Madison limestone without intercepting the Madison aquifer.

MODELING TRANSPORT AND RETENTION OF GRAPHENE OXIDE IN BIOCHAR MEDIA UNDER SUBSURFACE AQUATIC ENVIRONMENT

Md Sazadul Hasan, Venkataramana Gadhamshetty, and Mengistu Geza Department of Civil and Environmental engineering, South Dakota School of Mines and Technology [email protected] [email protected] [email protected]

Fixed-bed column studies were conducted using quartz sand, Biochar (BC), and BC- nZVI (BC surface modified with nanoscale zero-valent iron) in different configurations as a function of Ionic Strength (IS) relevant to the subsurface aquatic environment. Colloid filtration theory (CFT) was employed to develop mathematical models based on the one-dimensional convection-dispersion equation using breakthrough curves (BTCs). Three models accounted for no blocking, site-blocking, and depth-dependent (straining) blocking functions on the retention coefficients were applied. The inverse modeling was implemented to fit the attachment coefficient (Ka) and maximum solid-phase retention capacity (Smax) for all media. Results demonstrated the model considering site- blocking describe the BTCs well (R2 ~ 0.60-0.99) due to the limited attachment capacity of the media. Other two media exhibited 82 ~ 2.3E9-fold higher attachment efficiency compared to sand due to high porosity, roughness, and surface chemical properties. Higher Ka was observed in BC (0.62 vs 0.35) compared to BC-nZVI at 10 Mm IS. Owing to a lower Ka and higher Smax (6.47 vs 6.17), BC-nZVI displayed better performance in the long run at 10 mM IS. GO retention was influenced by aggregation and straining at higher IS. In contrast, higher Ka values were predicted in BC-nZVI (2.26 vs 0.07) at 0.1 mM IS primarily due to the attachment of GO onto nZVI where nZVI in BC pores was also favorable for the straining process. Employing fitted transport parameters extracted from the model (considering site-blocking), scenarios with an unlimited GO application were predicted via forward simulation. Model outputs indicated that with a 60 cm of depth BC and BC-nZVI require 6.62 and 8.57 days, respectively for a complete (C/C0 > 0.98) GO breakthrough at 10 mM IS where sand needs only 0.074 days. This study revealed that BC-nZVI would be an efficient filter media for GO retention under subsurface environmental conditions.

THURSDAY, APRIL 22, 2021 SESSION 3 8:00 – 10:00 A.M.

IMPACTS OF SEDIMENTATION ON MISSOURI RIVER RESERVOIRS AND FREE-FLOWING SEGMENTS

Tim Cowman South Dakota Department of Agriculture and Natural Resources Geological Survey Program [email protected]

The introduction of dams and reservoirs on the main stem Missouri River in the mid- nineteenth century has resulted in large amounts of sediment deposition in the reservoirs. The Lake Sharpe, Lake Francis Case, and Lewis and Clark Lake reservoirs have all been impacted by sediment accumulation. The headwaters area of Lewis and Clark Lake has been described as the “poster child” for sedimentation issues on large rivers of the United States. Resources that are currently being impacted or may be impacted in the future by sediment accumulation include infrastructure, such as roads and bridges, recreation areas, flow regulation, water supply intakes, hydropower generation, and reservoir storage capacity. Free-flowing segments of the river downstream of dams are also impacted. As most of the sediment is captured in the reservoirs, the free-flowing river strives to regain its sediment balance through bed and bank erosion. The erosion impacts can be seen at distances of tens of miles downstream from the dams. Near Yankton, South Dakota, bed erosion has exceeded 11 feet since Gavins Point Dam was closed off in 1955. Near Vermillion, South Dakota, some 30 miles downstream from Gavins Point Dam, bed erosion has lowered water tables and resulted in disappearing wetlands and backwaters on the floodplain adjacent to the river. Sediment management on the Missouri River is vital to sustaining the resources of this large river system. Attempts are being made on a local level to reduce sediment inflow to the river. Larger regional efforts are being evaluated by both government and non- government organizations to make a significant reduction in the sedimentation problem on the Missouri River.

ANALYSIS OF POTENTIAL ALTERNATIVE OPERATIONS FOR PACTOLA AND DEERFIELD RESERVOIRS

David M. Waterman and Rosemary C. Squillace South Dakota School of Mines and Technology [email protected] [email protected]

The Rapid Creek water system consists of Rapid Creek and the Deerfield and Pactola reservoirs. Outflow from the reservoirs are managed based on prescribed release rules and water orders from the City of Rapid City, in conjunction with the best available information regarding projected inflows. A systems operation model was developed for the two reservoirs using the U.S. Army Corps of Engineers’ software HEC-ResSim. The model allows different reservoir release rules to be explored through numerical simulation. Different alternatives were compared based on two primary metrics: (a) the volume of ‘spilled’ water, or water released without a specific purpose due to the conservation pool being full; and (b) the probability of the stored water volume dropping to dangerously low levels. The analysis was based on synthetic inflow time series generated from the 61 years of available inflow record using Monte Carlo methods. The results reveal that allowing the conservation pool to fluctuate over a broader range of elevations during years in which the conservation pool is nearly full can significantly reduce the volume of spilled water while maintaining the very low probabilities of experiencing future low storage volumes. This presentation summarizes the findings of a project completed in December 2019.

HYDRAULIC ANALYSIS OF FISH HABITAT RESTORATION OF RAPID CREEK DOWNSTREAM OF PACTOLA RESERVOIR

Anne Winckel SDSMT and RESPEC [email protected]

Scott Kenner SDSMT [email protected]

A high-resolution 2D HEC-RAS model was employed to define the hydraulic conditions in a 3,400 ft stretch of a cold water fishery in Rapid Creek below Pactola Dam in the Black Hills of South Dakota. Suitability index (SI) values were computed at every 2 ft by 2 ft grid cell using the depth and velocity suitability index curves for brown trout created by Raleigh, Zuckerman, and Nelson (1986). Weighted Usable Area (WUA) and Composite Suitability Index (SI) were used for two types of comparisons: a comparison over a range of flow rates, as well as with and without habitat improvement structures.

Flow rates of 7, 18, 38, and 80 ft3/s (0.2, 0.51, 1.1, and 2.3 m3/s) were modeled. It was found that increasing flow rates up to 38 ft3/s (1.1 m3/s) provided significant improvement in WUA (43% and 19% increases), while increasing flow rates above 38 ft3/s provided only a small increase (6% increase).

To quantify the impact in WUA provided by structures, the analysis was performed on two separate terrain models: one representing the channel after constructing habitat improvement structures, and one representing the channel without the structures. It was found that adding the structures did not significantly affect WUA within this reach, with a percent difference in WUA of -0.6% to 5.1%, and had a small area of influence.

It was also concluded that the impact on WUA with respect to depth and velocity is more significant when adjusting flow rate than adding these structures, and maintaining wintertime instream flow rates at 38 ft3/s (1.1 m3/s) or higher in this reach is recommended. Two-dimensional modeling can provide significant insight for the placement of physical habitat to enhance the value of improved habitat.

EXAMINING THE INFLUENCE OF CLIMATE CHANGE ON STREAM YIELD IN THE BLACK HILLS OF SOUTH DAKOTA

Lucas Graunke, Lisa Kunza, William Capehart, and Mengistu Nisrani South Dakota School of Mines and Technology [email protected] [email protected] [email protected] [email protected]

Water resources in the Black Hills provide multiple local recreational and economic benefits. Long-term stream monitoring data in the US and worldwide depict changes in average annual and seasonal stream yield, which can impact aquatic habitats and water quality. The main objectives of this project are 1) to model stream yield changes in response to two scenarios of projected climate change and 2) discern what changes in stream yield are observed and which climate change scenario alters stream yield more. Our selected watersheds are the upper reaches of Spring Creek, Battle Creek and French Creek, which share similarities in topography, land use and climate. Preliminary results show streamflow increases for all months in each watershed. The smallest increases are seen during late summer and fall, and the largest increases are during the winter. Data from Global Climate Models, which generate output using Representative Concentration Pathways 4.5 and 8.5, is used in the Soil and Water Assessment Tool to model stream yield. Climate change will continue to affect stream yield in the Black Hills and contribute to alterations in water quality and available water for industrial, agricultural, and recreational uses.

CHARACTERIZATION OF FACTORS AFFECTING GROUNDWATER LEVELS IN AND NEAR THE ROSEBUD INDIAN RESERVATION AND IN AND NEAR THE FORMER LAKE TRAVERSE INDIAN RESERVATION, WATER YEARS 1956–2017

Kristen Valseth U.S. Geological Survey [email protected]

The U.S. Geological Survey recently completed studies to characterize water-level fluctuations in observation wells relative to driving factors that affect water levels in and near the Rosebud Indian Reservation and in and near the historical 1867 boundary of the Lake Traverse Indian Reservation. Analyses included trend testing of precipitation and groundwater datasets in annual time steps for statistical significance using the Mann-Kendall test for probability values less than or equal to 0.10 (90 percent confidence level) and determination of trend magnitude using the Sen’s slope estimator. For both study areas, statistically significant upward trends were detected for annual precipitation for WY 1956–2017, which includes the longest available records for water- level measurements for each study area. Groundwater trends for observation wells were analyzed for three separate water-level parameters (annual minimum, median, and maximum) because wells are measured sporadically and data are biased towards more frequent measurements during periods of heaviest irrigation demand. Of 58 observation wells considered for the Rosebud study area, 28 wells had significant upward trends for at least one of the three water-level parameters, 11 wells had significant downward trends for at least one water-level parameter, and 19 wells did not have any significant trends. Of 76 observation wells considered for the Lake Traverse study area, 43 wells had significant upward trends for at least one water-level parameter, 8 wells had significant downward trends for at least one water-level parameter, and 25 wells did not have any significant trends. For both study areas, graphical analyses were conducted to provide qualitative indicators of proximal groundwater demand on groundwater levels. Downward trends in groundwater levels were concentrated in the central part of the Rosebud study area, generally in areas of major groundwater withdrawals; however, downward trends were spread sporadically throughout the Lake Traverse study area.

THURSDAY, APRIL 22, 2021 SESSION 4 10:00 A.M. – 12:00 P.M.

MESONET MONITORING OF SOIL MOISTURE AND SNOWPACK MONITORING IN THE UPPER MISSOURI RIVER BASIN

Nathan Edwards South Dakota Mesonet, South Dakota State University [email protected]

The state mesonets of South Dakota, Wyoming, Montana, North Dakota and Nebraska are being tasked by the US Army Corps of Engineers to provide improved monitoring in the Upper Missouri River Basin. The project will provide data for snow modeling, runoff forecasting and drought monitoring across a quarter million square miles at 500 weather stations equipped to measure soil moisture, precipitation and snow depth among other environmental variables.

FROM THE GROUND UP - MANAGING WATER FOR QUALITY AND QUANTITY

John McMaine Ag & Biosystems Engineering, South Dakota State University [email protected]

How we manage the landscape can have significant implications for local and downstream water quality and quantity. Two recently launched projects in eastern South Dakota are exploring the relationship between landscape management and water quality at the field scale as well as soil moisture risk at the field and watershed scales. The water quality project is funded by the South Dakota Nutrient Research and Education Council and focuses on nutrient load and concentration in tile drain outlets in eastern South Dakota. Around 25 outlets are being regularly sampled and water samples are analyzed for nitrate and ortho-phosphate. Flow rate is also recorded and load is calculated. The project objectives are to establish what the baseline is for potential nutrient loss from tile in eastern South Dakota and identify any potential risk factors, such as soil type, that could inform optimal placement of edge-of-field conservation practices.

The second project examines how agricultural management practices affect soil moisture risk at the field and watershed scale as well as the economic implications of improved soil moisture management and barriers/drivers to adoption of conservation practices. Twenty-five fields have been chosen to monitor for soil moisture for three growing seasons. These results will inform how management affects soil moisture risk and will also be used to calibrate a watershed-scale hydrologic and hydraulic model. Management within the landscape significantly affects water quality and water quantity. These two recently launched projects will aid in improved field and watershed management to reduce potential negative impacts to water resources.

IMAGE SEGMENTATION OF TILE DRAINAGE SYSTEMS USING U- NETS

Fleford Redoloza, Tanja Williamson, Alex Headman U.S. Geological Survey [email protected]

Tile drainage systems are a popular agricultural technique used for removing excess water from the soil. Permeable tiles and pipes are installed beneath the surface and are connected into networks designed to route water away from areas of interest. As more tile drainage systems are deployed since the 1800’s in the U. S., these agricultural structures have the overall effect of changing how groundwater aquifers are recharged. The influence of these structures can be better understood if the style and their spatial extent is known. This could be done by identifying and outlining these structures from satellite images. However, it is impractical to do this process manually. Instead, our research involves deploying machine learning methods to automate the process of segmenting these the tile drainage structures from satellite images. We have shown that U-Nets are a promising method for this task. U-Nets refer to a class of neural networks designed for the task of image segmentation. Given a set of satellite images with the tile drains manual traced out, we were able to train a U-Net model that could successfully outline tile drainage systems on satellite images it has never seen before. We characterize the uncertainty of the U-Net model and found that it can be used to coarsely estimate the spatial extent and area of tile drainage networks. We also developed a U-Net model capable of distinguishing between older topographic tile drainage networks versus modern densely patterned tile drainage networks.

INVESTIGATION OF MUSKINGUM ROUTING PARAMETERS IN NATURAL CHANNEL IN NORTH DAKOTAN RIVER UNDER SNOWMELT-INDUCED FLOODING CONDITIONS

Vida Atashi and Yeo Lim University of North Dakota [email protected] [email protected]

Hydrological processes related to snow occur in large regions on earth including North Dakota where runoff triggered by snowmelt is an important annual event. The Muskingum model is one of the most popular models for hydrologic channel flood routing. Despite of the simplicity of Muskingum equation, the real parameters of this equation have not been comprehensively explained. In this research, the parameters of Muskingum model are found using the basin characteristics representing the inlet and outlet of the channel reach for two station in Pembina River, North Dakota (Walhalla and Neche). The Muskingum flood routing method was applied to three flood years (2009, 2011 and 2017). The result derived are useful for hydrologic routing in channels and allow better prediction of the hydrologic conditions of watershed runoff at outlet location.

IMPROVING WATER QUALITY WITH THE SCENARIO APPLICATION MANAGER (SAM)

Seth Kenner RESPEC [email protected]

When water quality is impaired, watershed decision makers need to choose management practices that lead to the greatest improvements in water quality while balancing costs and practicality. The Scenario Application Manager (SAM) is a watershed-scale, decision-support tool. The SAM for each major watershed consists of a Geographic Information System (GIS) for site selection and evaluation, a Hydrologic Simulation Program – Fortran (HSPF) model application to simulate pollutant fate and transport, and the best management practice (BMP) database. An HSPF model application has been developed for nearly every major watershed in the state of Minnesota, and as such, SAM is available to the decision makers in every major watershed with an HSPF model. SAM assists in developing custom strategies for protection, prioritization, and BMP implementation planning by combining individual and/or suites of scenarios to selected subwatersheds throughout each major basin. It simulates the expected instream water quality changes resulting from each simulated management practice. Land use changes for what-if scenarios and adjustments to point source time-series data for National Pollutant Discharge Elimination System (NPDES) permit development can also be represented. The combination of the graphical interface, a state-accepted watershed model, practical BMPs, flexible scenario development, and cost optimization bridges a gap between watershed characterization by water resource engineers and the water resource managers who ultimately develop implementation and pollutant reduction plans.