Baseflow Variability Due to Changes in Climate, Basin Characteristics, and Groundwater Withdrawals in the State of Wisconsin, USA

ABSTRACT BASEFLOW VARIABILITY DUE TO CHANGES IN CLIMATE,BASIN CHARACTERISTICS, AND GROUNDWATER WITHDRAWALS IN THE STATE OF WISCONSIN, USA bySusan Borchardt The University of Wisconsin-Milwaukee, 2022 Under the Supervision of Professor Woonsup Choi In Wisconsin, the number of high-capacity wells has increased substantially, and concerns have been raised about their impact on both groundwater levels and streamflow. At the same time Wisconsin’s climate has been changing, and both the annual precipitation (5%) and temperature (1.5oC) have been trending upward over the last 68 years and both are predicted to increase into the future. This study attempted to demonstrate the simultaneous effects of climate change, physical basin changes and changes to the groundwater withdrawal rate from high-capacity wells by employing both analytic methods and simulation models. Linear regression was used to determine how variables representing climate, land use, soil characteristics, and groundwater withdrawals would affect baseflow variability. While double-mass curve analysis was used to find that twenty out of the thirty-five basins studied exhibited a deviation in the slope when the cumulative value of precipitation was plotted against the cumulative value of baseflow suggesting an anthropogenic variable was affecting baseflows, most likely groundwater withdrawals. Panel data analysis (PDA) was then used to evaluate the simultaneous effects of climate, withdrawal rate, and physical basin variables on baseflow variability across the state. The PDA found that the climate variables (precipitation and temperature) were significant in explaining the temporal variability of baseflow, whereas land use and the drainage conditions were important in explaining the spatial variability of baseflow as expected. But the groundwater withdrawal was not, which was not expected. The Soil & Water Assessment Tool (SWAT) and the United States Geological Survey’s Modular Hydrologic Model (MODFLOW) were used to simulate changes in hydrology in a single basin in the state that has experienced declining baseflows over the last 30 years but steady population numbers and land use percentages over the same period. Using the variables found to affect baseflow (climate, land use, and soil characteristics), SWAT was used to simulate the change in the recharge rate, and then using the withdrawal rate from high-capacity wells, MODFLOW was used to simulate the change in hydraulic head. The SWAT model predicted that future increases in Wisconsin’s annual precipitation of approximately 7.5% will cause increases in both groundwater recharge (16.74%) and streamflow (14.13%). The future increases in temperature of 2.2–3.3oC by the middle of the 21st century, however, are predicted to leave the state with a net reduction in both streamflow (–23.39%) and groundwater recharge (–19.63%). In addition, the MODFLOW model predicted a mean head elevation decrease of over 2 meters due to increased predicted temperatures, this is despite predicted increases in annual precipitation and an additional decrease in groundwater elevation surrounding high-capacity wells due to predicted increases in annual withdrawal rate. Overall, analytically the most important variable in determining the variability of streamflow is the amount of annual precipitation, but the modeling portion of the study showed that the predicted increases in temperature will ultimately lead to decreases in the available fresh water in the study area. This study also highlights that if the escalating use of irrigation for Wisconsin’s agriculture outpaces the increases in annual precipitation, declines in stream baseflow will result. The study also predicted that some of these decreases can be mitigated by abandoning just a select number of high withdrawing wells. Keywords: Baseflow, Groundwater, High-capacity wells, Double-mass curve analysis, SWAT, MODFLOW, Streamflow, Aquifer, Regression mode

Variation of Groundwater Divides during Wet and Dry Years in the Wolf River Basin, Northeastern Wisconsin

Groundwater divides and surface-water divides do not always coincide, and groundwater divides are not as easy to detect as surface-water divides. Groundwater divides are also dynamic, moving in response to environmental and anthropogenic stresses. This study will investigate how different hydrological stresses can change the size and shape of the study basin and whether the stresses together mitigate or intensify the basin’s response. This study looks at three factors that may affect the size and shape of the Wolf River basin: annual precipitation, soil permeability, and the presence of high-capacity wells. This study examined four groundwater basins that represent the groundwater contributing to the baseflow at the stream-flow gauge at Langlade, on the Wolf River in northeastern Wisconsin. The study consisted of two wet years (1985 and 2015) and two dry years (1989 and 2008); the two different time periods represent before and after extensive use of high-capacity wells, pre-1990 and post-2000. The study found an overall lowering of the groundwater elevation, attributed to the hydrological stresses created by both decreases in precipitation and increases in the number of high-capacity wells in the area. The lowering of the water table allowed groundwater flow to follow bedrock topography rather than surface topography leading to increases in the groundwater basin’s area. This study highlights that the effects of one hydrological stress (groundwater pumping) can be amplified by another hydrological stress (decreased annual precipitation), resulting in similar numbers of wells having a significantly greater effect on groundwater in dry years than in wet years. This knowledge can help water-resource managers predict basin changes in similar basins

High Capacity Wells and Baseflow Decline in the Wolf River Basin, Northeastern Wisconsin

The baseflow of the Wolf River (drainage area of 1 200 km2) in northeastern Wisconsin has declined by over 30% during the last thirty years, whereas climatic, land cover, and soil characteristics of the basin have remained unchanged. Because groundwater basins do not always coincide with surface water basins, estimating groundwater discharge to streams using variables only pertinent to the surface water basin can be ineffective. The purpose of this study is to explain the decline in the baseflow of the Wolf River by developing a multiple regression model. To take into account variables pertaining to the groundwater basin, withdrawal rates from high capacity wells both inside the Wolf River basin and in two adjacent basins were included in the regression model. The other explanatory variables include annual precipitation and growing degree days. Groundwater discharge to the river was calculated using streamflow records with the computer program Groundwater Toolbox from the United States Geological Survey. Without the high capacity wells data, the model only explained 29.6% of the variability in the groundwater discharge. When the high capacity wells data within the Wolf River basin were included, r2 improved to be 0.512. With the high capacity wells data in adjacent basins, r2 improved to be 0.700. The study suggests that human activity taking place outside of the basin has had an effect on the baseflow, and should be taken into account when examining baseflow changes

Viruses in nondisinfected drinking water from municipal wells and community incidence of acute gastrointestinal illness.

BackgroundGroundwater supplies for drinking water are frequently contaminated with low levels of human enteric virus genomes, yet evidence for waterborne disease transmission is lacking.ObjectivesWe related quantitative polymerase chain reaction (qPCR)-measured enteric viruses in the tap water of 14 Wisconsin communities supplied by nondisinfected groundwater to acute gastrointestinal illness (AGI) incidence.MethodsAGI incidence was estimated from health diaries completed weekly by households within each study community during four 12-week periods. Water samples were collected monthly from five to eight households per community. Viruses were measured by qPCR, and infectivity assessed by cell culture. AGI incidence was related to virus measures using Poisson regression with random effects.ResultsCommunities and time periods with the highest virus measures had correspondingly high AGI incidence. This association was particularly strong for norovirus genogroup I (NoV-GI) and between adult AGI and enteroviruses when echovirus serotypes predominated. At mean concentrations of 1 and 0.8 genomic copies/L of NoV-GI and enteroviruses, respectively, the AGI incidence rate ratios (i.e., relative risk) increased by 30%. Adenoviruses were common, but tap-water concentrations were low and not positively associated with AGI. The estimated fraction of AGI attributable to tap-water-borne viruses was between 6% and 22%, depending on the virus exposure-AGI incidence model selected, and could have been as high as 63% among children < 5 years of age during the period when NoV-GI was abundant in drinking water.ConclusionsThe majority of groundwater-source public water systems in the United States produce water without disinfection, and our findings suggest that populations served by such systems may be exposed to waterborne viruses and consequent health risks

Human Influences and Decreasing Synchrony between Meteorological and Hydrological Droughts in Wisconsin Since the 1980s

Hydrological droughts are important for agriculture and other human activities such as navigation and groundwater pumping, so it is necessary to understand their characteristics at various temporal and spatial scales. This study aims to examine the characteristics of hydrological droughts and their propagation from meteorological droughts across Wisconsin. Hydrological droughts were identified for twenty-four U.S. Geological Survey streamflow monitoring sites using the 20th percentile threshold level for each calendar day. Meteorological droughts were identified in the same way using daily precipitation data. Drought events of both types were identified for the period from 1980 to 2018, and the drought in 2012 was examined in detail. Our results indicate that (1) unlike meteorological droughts, hydrological droughts tend to occur more frequently in recent years; (2) characteristics of hydrological droughts are not correlated with those of meteorological droughts or annual precipitation; (3) there are generally three drought regions in Wisconsin showing different drought trends and propagation characteristics; and (4) groundwater withdrawal from unconfined aquifers has exacerbated hydrological droughts. In conclusion, hydrological droughts have become less synchronous with meteorological droughts, which will make drought early warning more challenging. The study sheds light on drought characteristics and propagation in relation to catchment characteristics and human activities

Effects of Climate, Basin Characteristics, and High-Capacity Wells on Baseflow in the State of Wisconsin, United States

When it comes to water resources management, it is critical to understand the factors that affect baseflow processes. Declines in baseflow due to increased use of the groundwater from unconfined aquifers is well documented, but that is not the case for confined aquifers. Furthermore, since the groundwater basin size and shape can be different than the surface water basin, the use of the surface basin to determine well withdrawal rates can affect baseflow and be problematic. This study used the variables determined to be related to baseflow variability (precipitation, temperature, drainage class, available storage, land use, and slope) and the withdrawal rates of wells located within the study basins to create regression models for the state of Wisconsin, United States. We find that: (1) precipitation and temperature variable are significant in explaining the temporal variability of baseflow, whereas land cover variables are important when the temporal variability is not considered; (2) evaporation and soil drainage are important in basins over unconfined aquifers, whereas precipitation the most significant over confined aquifers; (3) whether to use surface water or groundwater divides to delineate basins matters in particular conditions, and (4) groundwater withdrawal rates do not significantly affect baseflow when using statistical analysis. Therefore, analyzing baseflow should be supplemented by a process-based model for the effects of groundwater withdrawals

High Capacity Wells and Baseflow Decline in The Wolf River Basin, Northeaster Wisconsin (USA)

The baseflow of the Wolf River (drainage area of 1,200 km2) in northeastern Wisconsin (USA) has declined by over 30% during the last thirty years, whereas climatic, land cover, and soil characteristics of the basin have remained unchanged. Because groundwater basins do not always coincide with surface water basins, estimating groundwater discharge to streams using variables only pertinent to the surface water basin can be ineffective. The purpose of this study is to explain the decline in the baseflow of the Wolf River by developing a multiple regression model. To take into account variables pertaining to the groundwater basin, withdrawal rates from high capacity wells both inside the Wolf River basin and in two adjacent basins were included in the regression model. The other explanatory variables include annual precipitation and growing degree days. Groundwater discharge to the river was calculated using streamflow records with the computer program Groundwater Toolbox from the United States Geological Survey. Without the high capacity wells data, the model only explained 29.6% of the variability in the groundwater discharge. When the high capacity wells data within the Wolf River basin were included, r2 improved to be 0.512. With the high capacity wells data in adjacent basins, r2 improved to be 0.700. The study suggests that human activity taking place outside of the basin has had an effect on the baseflow, and should be taken into account when examining baseflow changes

Global patterns and drivers of alpine plant species richness

Aim Alpine ecosystems differ in area, macroenvironment and biogeographical history across the Earth, but the relationship between these factors and plant species richness is still unexplored. Here, we assess the global patterns of plant species richness in alpine ecosystems and their association with environmental, geographical and historical factors at regional and community scales. Location Global. Time period Data collected between 1923 and 2019. Major taxa studied Vascular plants. Methods We used a dataset representative of global alpine vegetation, consisting of 8,928 plots sampled within 26 ecoregions and six biogeographical realms, to estimate regional richness using sample‐based rarefaction and extrapolation. Then, we evaluated latitudinal patterns of regional and community richness with generalized additive models. Using environmental, geographical and historical predictors from global raster layers, we modelled regional and community richness in a mixed‐effect modelling framework. Results The latitudinal pattern of regional richness peaked around the equator and at mid‐latitudes, in response to current and past alpine area, isolation and the variation in soil pH among regions. At the community level, species richness peaked at mid‐latitudes of the Northern Hemisphere, despite a considerable within‐region variation. Community richness was related to macroclimate and historical predictors, with strong effects of other spatially structured factors. Main conclusions In contrast to the well‐known latitudinal diversity gradient, the alpine plant species richness of some temperate regions in Eurasia was comparable to that of hyperdiverse tropical ecosystems, such as the páramo. The species richness of these putative hotspot regions is explained mainly by the extent of alpine area and their glacial history, whereas community richness depends on local environmental factors. Our results highlight hotspots of species richness at mid‐latitudes, indicating that the diversity of alpine plants is linked to regional idiosyncrasies and to the historical prevalence of alpine ecosystems, rather than current macroclimatic gradients

Extensive Genetic Diversity, Unique Population Structure and Evidence of Genetic Exchange in the Sexually Transmitted Parasite Trichomonas vaginalis

The human parasite Trichomonas vaginalis causes trichomoniasis, the world's most common non-viral sexually transmitted infection. Research on T. vaginalis genetic diversity has been limited by a lack of appropriate genotyping tools. To address this problem, we recently published a panel of T. vaginalis-specific genetic markers; here we use these markers to genotype isolates collected from ten regions around the globe. We detect high levels of genetic diversity, infer a two-type population structure, identify clinically relevant differences between the two types, and uncover evidence of genetic exchange in what was believed to be a clonal organism. Together, these results greatly improve our understanding of the population genetics of T. vaginalis and provide insights into the possibility of genetic exchange in the parasite, with implications for the epidemiology and control of the disease. By taking into account the existence of different types and their unique characteristics, we can improve understanding of the wide range of symptoms that patients manifest and better implement appropriate drug treatment. In addition, by recognizing the possibility of genetic exchange, we are more equipped to address the growing concern of drug resistance and the mechanisms by which it may spread within parasite populations