Goals and Objectives- Intensive groundwater withdrawal for irrigation over the past century has resulted in significant declines in groundwater levels across the Great Plains, and in rivers with high groundwater connectivity, to decreased annual discharge. Lowered flows have led to decreased dispersal opportunities among the spawning, rearing, and refuge habitats vital for the persistence of native fish populations. My research focuses on:
-Linking fish ecology to groundwater hydrology in a western Great Plains stream to make recommendations for conservation and management under climate change and drought.
-Measuring the spawning phenology and recruitment of under-studied Great Plains fishes across spatial scales.
Study Area and Design- My research is designed to quantify the response of fishes and fish habitat to groundwater withdrawal and drought across multiple spatial scales. My study area is the groundwater-fed Arikaree River in Eastern Colorado, which serves as an important refuge for several plains fish species with declining distributions in Colorado, including the brassy minnow (Hybognathus hankinsoni) and orangethroat darter (Etheostoma spectabile). My primary study sites are three 6.4-km segments along the Arikaree River that represent a gradient in flow and intermittency from upstream (wet) to downstream (dry). Within each segment, I have delineated reaches based upon channel morphology and geomorphology. However, many processes that influence the distribution of habitats along a Great Plains riverscape are patchy (e.g., summer thunderstorms, groundwater connectivity) and create habitats (e.g., refugia) that would be missed by reach based randomized sampling. Therefore, much of my sampling is census based across intermediate scales. This design allows me to:
-Identify and georeference all habitats within each segment which aids in proper random selection of channel units for more detailed sampling (e.g., population estimates, detailed habitat surveys).
-Measure total habitat area within each segment, and count the number of habitats within different categories across all segments (e.g., pools, backwaters)
Methods and Expected Outcomes-My dissertation research is divided into two major components that focus on increasing our understanding of plains fishes using methods that apply both theoretical and applied concepts in fisheries science and ecology. Specifically my methods are to:
Method 1: Measure the dynamics of wetting and drying of fish habitats and link this to shallow groundwater stage along the riverscape across multiple years.
Outcome 1: Use these groundwater and fish habitat data to develop a groundwater-surface water model that can be used to predict habitat quantity within the Arikaree Basin into the future, based upon scenarios of land-use (e.g., increased or decreased irrigation pumping) and climate change.
Method 2: Sample both larval and adult plains fishes and their habitats across multiple scales to assess critical life history and habitat requirements in the context of pumping and drought.
Outcome 2: As little is known about the spawning phenology and recruitment dynamics of plains fishes I hope to gain an understanding of basic life history information for plains fishes and to use this information to make informed conservation and management recommendations.
Loss of critical habitats due to stream dewatering and the subsequent negative effects on native fishes are not unique to eastern Colorado. Managers across the Great Plains are challenged to address this issue, and I anticipate that the methods I develop for modeling groundwater and fish habitat will be used in other similar groundwater dependent systems for conservation purposes. Overall, I hope to integrate what I discover through my research to aid in making recommendations for conservation and management of native fishes in the Arikaree River basin in the context of pumping and drought.
