NIEMANN RESEARCH GROUP
Glacier Creek Watershed, Colorado (Sonja Wilkinson)
Water system map
Access to properly functioning water and sanitation systems is critical to public health and community development. Approximately 30% of the world's population lacks access to safely managed drinking water systems, and 55% lacks access to safely managed sanitation systems. Because most people who lack access live in rural areas of the majority world, improving access requires implementation of sustainable, low-cost, and reliable systems. It also requires development methods that are community-driven and broadly beneficial. We are working to train engineers and development workers in appropriate water, sanitation, and hygiene (WASH) methods. We also provide technical guidance through various organizations for WASH projects around the world.
  • Kijabe, Kenya. Provided technical guidance focused on improving drinking water quality and reliability as well as sustainable wastewater disposal for an pediatric orthopedic hospital campus (2021)
  • El Pital, El Salvador. Provided technical guidance for senior design project focusing on the design of water supply systems for a small rural community (2018 – 2019)
  • Belmopan, Belize. Developed water supply and sanitation master plans for a K-12 school campus (2018)
  • Lesoit, Tanzania. Planned water supply system for a small Maasai community (2017)
  • Murcia, Philippines. Developed water supply and wastewater master plans for a proposed orphanage campus (2017)
  • Chogoria, Kenya. Provided technical guidance for water supply and wastewater master plans for a hospital complex and associated housing (2016)
  • Gulbarga, India. Provided technical guidance for water and wastewater systems for a goat farm cooperative (2015)
  • Bomet, Kenya. Provided technical guidance and review for an evaluation of water and wastewater systems for a hospital complex (2013 – 2015)
  • Nkoltang, Gabon. Developed water and wastewater master plans for large campus including an orphanage, schools, medical clinic, housing for widows/widowers, and other facilities (2011)
  • Kijabe, Kenya. Developed 10-year master plan for water and wastewater systems of a large hospital complex and associated community (2010 – 2014)
  • La Laguneta and El Chile, El Salvador. Provided technical guidance for Engineers Without Borders project to improve water supplies for two small communities (2005 – 2009)
  • Zacapa, Guatemala. Assessed condition and planned improvements for the water supply system of orphanage campus and assisted with preliminary design of wastewater improvements (2002)
Soil moisture maps
Soil moisture is arguably the most central variable in hydrology because it affects both the land-surface energy balance and water balance. It impacts the production of runoff at the ground surface, transpiration rates from crops and other vegetation, and recharge to shallow aquifers. Unfortunately, direct measurement of soil moisture patterns at the spatial scale of most practical applications is difficult. In-situ methods observe soil moisture only at the probe locations, and interpolating between such measurements is often unreliable. In contrast, satellite remote sensing methods typically observe soil moisture at very coarse spatial resolutions and must be downscaled to reach adequate resolutions for many applications. We are studying the physical processes that control soil moisture, statistical properties of soil moisture patterns, and methods to interpolate and downscale soil moisture observations. As part of this effort, we have developed a patented soil moisture downscaling method that is now used commercially. Understanding the spatial patterns and temporal dynamics of soil moisture benefits water resources planning, flood forecasting, land management, and other applications.
Landslide location maps
Extreme precipitation events and associated floods are critical considerations for infrastructure design and public safety. For instance, hydrologic models are used in dam safety evaluations to determine the flow rates that spillways must safely convey. The predictions from such models involve significant uncertainty, particularly in mountainous basins, due to difficulties in estimating realistic design storms, the active streamflow production mechanisms, and the flood-wave propagation rates. Extreme precipitation can also initiate landslides and debris flows in mountainous watersheds. For example, a September 2013 storm caused more than 1100 debris flows in the Colorado Front Range. We are developing modeling approaches that more accurately simulate runoff production for major flood events in Colorado’s mountainous basins. These modeling approaches are being used by Colorado Dam Safety as the basis for their new hydrologic modeling guidelines. We are also developing probabilistic tools to predict landslide initiation and runout locations using downscaled soil moisture patterns, and we are formulating new approaches to rapidly predict flood inundation areas. Our flood inundation mapping methods are being used real-time by the Army Corps of Engineers over large portions of the globe.
Snowpack maps
Snowpack is an important source for water supply in many parts of the world. In the western U.S., for example, runoff from snowmelt provides a large majority of annual water supplies. Rain on snowpack can also produce major floods, and the presence of frozen ground can impede infiltration and enhance flood production. Both snowpack and frozen ground are often heterogeneous within watersheds due to spatial variations in the topography, ground cover, and soil properties. Snowpack may also be affected by wildfires, which are becoming more common in the West. We are analyzing the response of snowpack to wildfires and developing improved methods to model the spatial and temporal patterns of snowpack and frozen ground in watersheds and their responses to wildfires. These methods are expected to improve the accuracy of water management tools and flood forecasting procedures.
Different channel network structures
A key element in watershed modeling is transforming the runoff that is produced across a watershed into a streamflow hydrograph at the watershed outlet. Traditional lumped models neglect explicit representation of the basin structure in modeling this transformation, while fully distributed models use cumbersome approximations of the St. Venant equations. We are exploring an intermediate approach called spatially-distributed travel time models. This approach explicitly represents the flow paths within the basin and moves the flow using travel times derived from the St. Venant equations. Thus, it can incorporate the effects of different channel network structures or even stormwater gutters and pipes. However, it does not require a numerical solution of the St. Venant equations. This research is expected to fill a gap in current modeling capabilities and broaden the range of practical applications that can be modeled for both natural and urban basins.
Evapotranspiration map
Many irrigated agricultural regions around the world face challenging water problems ranging from groundwater depletion to waterlogging and salinization associated with shallow water tables. Shallow water tables can also increase evapotranspiration from uncropped areas, which may represent a significant nonbeneficial consumptive use of water. Remote sensing methods are excellent resources for confronting these problems from field to regional scales. We are researching the use of optical and thermal remote sensing for estimating evapotranspiration and soil moisture in agricultural regions. We are also using NASA’s Gravity Recovery and Climate Experiment (GRACE) mission to explore groundwater depletion in regions that rely on groundwater. Ultimately, this research is expected to improve our understanding of the water balance in agri-ecological systems and numerical models that are used to evaluate potential solutions to groundwater depletion, waterlogging, and salinization problems.
Uncertainty estimates of sediment model
Many water agencies face decisions that involve the potential for economic losses, environmental impacts, and even loss of life if made incorrectly. These decisions are often based on the results of models that simulate watershed hydrology, channel flow, and/or sediment transport. However, the predictions from these models include substantial uncertainty. We are developing practical tools to quantify and ultimately reduce the uncertainty associated with hydrologic, hydraulic, and geomorphic models. These tools aim to identify and characterize uncertainties due to the assumed mathematical structure of the model as well as the uncertainty due to parameter estimation and model inputs. Our uncertainty estimation methods are used by the U.S. Bureau of Reclamation. Ultimately, these tools could result in more reliable predictions and more efficient designs of water infrastructure.
Illustration of scaling invariance
River basin topography has a very interesting property: it often appears similar when viewed at different magnifications. Without an indication of scale, it is difficult to determine whether a photograph of a river basin displays one hundred square kilometers or ten thousand square kilometers. This property is known as scaling invariance and is closely related to fractals and chaos. Many hydrologic variables exhibit this tendency including precipitation rates, soil moisture patterns, and channel networks. In fact, a wide variety of natural objects have fractal geometry. Scaling invariance is useful to hydrologists because it statistically relates the properties of small features to those of large features. Thus, it can help characterize, simulate, and interpolate hydrologic variables. We are examining scaling invariance of hydrologic and geomorphologic phenomena. Specifically, we are quantitatively characterizing the scaling invariance, understanding its dynamic origin, and exploring deviations from scaling.
Simulated river basins
One of the more exciting advances in geomorphological research is the development of sophisticated computer models that simulate the evolution of river basins over long periods of time. These models successfully reproduce many empirical features of river basin topography including dendritic river networks, concave profiles of stream courses, and convex profiles of hillslopes. These models can be used to understand the long-term impacts of climate and land-use changes, as well as the movement of sediment and long-lived pollutants in basins. We are developing better representations of hydrologic processes in these models and studying the role these processes play in landscape evolution.
Graphs of sensitivity of runoff and groundwater discharge
Climate change is among the top concerns for water resource managers around the world. The ongoing increases in atmospheric greenhouse gas concentrations are expected to impact air temperatures, precipitation patterns, snowpack amounts, evapotranspiration rates, and other aspects of the hydrologic cycle. Furthermore, climate change might also lead to more frequent natural disasters such as floods and wildfires. We are exploring the impacts of climate change on regional water balance and the expected availability and reliability of water resources.