Grantee Research Project Results
Final Report: Ecosystem Thresholds and Alternate States In Great Plains Rivers and Streams: Cascading Effects of Anthropogenic Hydrologic Disturbance
EPA Grant Number: R832446Title: Ecosystem Thresholds and Alternate States In Great Plains Rivers and Streams: Cascading Effects of Anthropogenic Hydrologic Disturbance
Investigators: Dodds, Walter , With, Kimberly A. , Koelliker, James , Gido, Keith
Institution: Kansas State University
EPA Project Officer: Packard, Benjamin H
Project Period: April 1, 2005 through July 10, 2008
Project Amount: $299,566
RFA: Exploratory Research: Understanding Ecological Thresholds In Aquatic Systems Through Retrospective Analysis (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
We planned to document the dramatic shift in the hydrologic state of Great Plains rivers and streams and how this has produced a biotic state change in this system. This hydrologic change results from human alteration of surface water flow through agricultural diversion, groundwater pumping, construction of small impoundments, and changing cultivation techniques.
Summary/Accomplishments (Outputs/Outcomes):
Ecological thresholds that lead to alternative community states can be exceeded through gradual perturbation or as a result of sudden disturbance. Such regime shifts have been demonstrated for lakes, oceans, and several terrestrial environments; however, it is unclear whether and how alternate regimes develop in naturally dynamic stream systems. We document a hydrologic regime shift in Kansas streams resulting from dramatic water and land use changes since 1880. Stream flow, both surface runoff and baseflow, in the major river networks in western Kansas are declining over the decades despite the slightly increasing precipitation trend. There is also an increased number of no-flow or flow below a threshold for vertebrate species in several stream gauges. The pattern of changes in the stream flow differed from the eastern to the western regions of the state, although it was evident that anthropogenic activities were the major factor.
Under the project, the hydrology group was tasked to address the objective of linking anthropogenic activities to the disconnection of streams and rivers under given precipitation regime. Specifically, to detect hydrologic state changes in the streams, determine the cause, and to provide support to the fish group in matters related to hydrology. Although it was first envisioned to conduct hydrologic simulation modeling, the sampling density of the fish data would not support the scale of modeling.
There are several hypotheses on hydrology that were addressed in the project. First, we hypothesized streamflow pattern was less in the eastern compared to the western portion of Kansas. Analysis shows that both the median and the low flow pattern are different in both regions. Stream flow in the western region of the state is consistently declining while in the eastern region it is increasing. Second, we hypothesized the number of no-flow days (below a threshold for vertebrate species) is increasing. At least in western Kansas, the trend is increasing with some streams having more than 50 consecutive days without flow. For the third hypothesis, we expected that baseflow is decreasing. Again, western Kansas showed a downward trend in the baseflow and total runoff. The fourth and last hypothesis, was that humans cause the hydrologic stage changes. Anthropogenic activities were the evident cause of the changes. This included groundwater extraction and water use, land use, and adoption of water conservation practices. Each factor behaves differently between flow regimes and across the regions of the state.
We hypothesized that these abiotic regime shifts, coupled with species introductions, facilitated homogenization of fish communities and shifted the system from predominantly lotic (flowing water) to lentic (still water) species in four system-wide perturbations: increased sediment supply from agriculture (1880-1950s); habitat fragmentation from reservoir construction (1950s-1960s); streamflow decreases from increasing groundwater withdrawal (late1960s-present); and the spread of invasive fishes (1950s to present). We uncoupled the response of each perturbation by comparing fish occurrence records from a 118-year period (1885-2003) across four major river basins differing in the magnitude and timing of human impact. The spatial and temporal unevenness of historical presence-absence records was resolved using Monte Carlo re-sampling to quantify changes in community structure (Jaccard’s similarity, J) and the frequency of occurrence of individual species (logit regression). We observed a similar restructuring of the fish community across river basins that, surprisingly, was primarily driven by increases in lentic species with only a few declines lotic species. The timing of these changes differed between the basins. Fish communities changed gradually in the Smoky Hill basin that has been heavily impounded since the 1960s. Changes in the fish communities of the upper Arkansas River basin were more abrupt after the 1970s, and were associated with reductions in stream discharge. Interacting effects of impoundment, groundwater withdrawals, and invasive species, as identified by our retrospective analysis, highlight the potential complications for recovery of these fish communities to a previous state, even if natural flow regimes are restored.
We did additional retrospective analyses to find thresholds of water quality and how those might influence biotic integrity. One project was a collaboration with Eric Banner of the Kansas Department of Health and Environment. He found that while mean instream concentrations of total phosphorus depend upon land use, downstream phosphorus loading was highly dependent on discharge events. There is a threshold of discharge in many Kansas watersheds above which phosphorus concentration increases. We could not identify specific processes in addition to discharge correlated to this breakpoint.
In a related project we used data from Kansas, Missouri, Nebraska and Iowa to show the relationship between nutrient concentration and macroinvertebrate diversity. We found that macroinvertebrate diversity declines sharply as nutrients increase. Primary consumer and not predator diversity decreases to a point and then eventually levels off at a lower level. The putative mechanism for this pattern is that primary consumers are sensitive to changes in the stoichiometry of their food, and eutrophication alters this stoichiometry.
Journal Articles:
No journal articles submitted with this report: View all 20 publications for this projectSupplemental Keywords:
Midwest, watersheds, sensitive populations, assessment, habitat, regionalization., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Aquatic Ecosystem, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, anthropogenic stress, estuarine research, species interaction, ecological thresholds, biodiversity, biotic complexity, anthropogenic impact, ecosystem indicators, modeling ecosystem change, aquatic ecosystems, water quality, Great Plains Rivers, ecosystem stress, riverine ecosystems, trophic interactions, ecosystem responseRelevant Websites:
http://www.k-state.edu/doddslab/ Exit
http://www.k-state.edu/fishecology/ Exit
http://www.k-state.edu/withlab/ Exit
http://www.k-state.edu/ksaquaticgap/ Exit
http://www.k-state.edu/ecoforecasting/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.