- Christopher L. Dutton
Christopher L. Dutton – Yale University
Spatial and temporal dynamics of hypoxic floods and fish kills in a tropical river
Hypoxia in rivers is uncommon due to the high rates of reaeration in flowing waters, and when it does occur, it is typically associated with high anthropogenic nutrient loading. Hypoxic floods can be catastrophic for river biota, often leading to widespread fish kills or other alterations in fish community composition and behavior.
I have been documenting frequent hypoxic floods (13 in 3 years) and fish kills (5 in 9 years) in the Mara River, East Africa, and my research has shown they are caused by the flushing of hippopotamus pools. There are over 4000 hippopotami in the Kenyan portion of the Mara River bringing in over 3500 kg of organic carbon into the aquatic ecosystem each day. I have shown that hippo pools within the 3 tributaries of the Mara become anoxic under low discharge, and increases in discharge flush out the hippo pools and carry a hypoxic pulse of water through the river downstream. However, the spatial and temporal dynamics of these hypoxic floods remain unknown.
My research aims to understand the drivers of variability in these hypoxic floods and how these hypoxic floods are propagated downstream. This understanding will be critical to predicting how the frequency and intensity of these events will be influenced by climate and land use change. Differences in the degree of hypoxia across different flood events are likely driven by differences in the time since hippo pools in a given area have been flushed out and the size of the rainfall event driving the flood. Because rainfall in the Mara region is highly localized within and among catchments, and the biogeochemistry that causes hypoxia can vary among pools and tributaries, understanding these dynamics requires fine scale spatial and temporal data on precipitation patterns across the catchment. To document the origin of hypoxic floods, we need to understand drivers of their variability and how they propagate through the river network. I will document hippo pool biogeochemistry and the discharge and dissolved oxygen (DO) response of the tributaries and main stem of the Mara River in response to the rainfall intensity and frequency from each sub-catchment of the Mara.
I will install a METER ATMOS 41 weather station in each of the three sub-catchments of the Mara River to monitor rainfall intensity, frequency and duration. I will continue to document the occurrence of hypoxic flood events in the Mara River with a water quality sonde installed downstream of all the hippo pools. I will also continue to map and survey the biogeochemistry of all hippo pools (~ 20-30) within the 3 sub-catchments of the Mara. I will model the degree of hypoxia in each flood event as a function of hippo pool biogeochemistry, time since last flushing and the timing and quantity of rainfall within each sub-catchment.
- Leena Shevade
Leena Shevade – Drexel University
Effect of plant root configuration on the performance of urban decentralized green stormwater management facilities due to spatiotemporal variation of field measurements of effective saturated hydraulic conductivity
Often a constant infiltration rate is assumed when designing green infrastructure (GI) sites. However, various studies suggest that the infiltration rate is dynamic and varies spatially and temporally during wet weather events. This research study will assess the effect of root zone configuration (both type and density) on the spatial variability of field saturated hydraulic conductivity values (Kfsat) using METER’s SATURO infiltrometer within the site. The study will also compare Kfsat and the unsaturated hydraulic conductivity (Kfs) measured with METER’s MiniDisk Infiltrometer values under different hydrologic conditions, and over three growing seasons.
The research will be performed on four, fully monitored urban GI sites with established vegetation. The results will be statically analyzed to derive generalizable rules reducing in-situ GI monitoring needs, and to calibrate 2D/3D models.
The proposed research aims to assess the effect of root zone configuration (both type and density), and the effect of ponding and inflow depths on the infiltration performance of urban GI.
- Katie Marcacci
Katie Marcacci – University of Tennessee – Knoxville
Influence of Plant Roots and Mycorrhizal Hyphae on Soil Hydraulic Parameters
The proposed research will focus on how plant roots and mycorrhizal hyphae impact soil hydraulic properties. Laboratory experiments will be performed to measure saturated hydraulic conductivity (KSAT) and soil water retention (HYPROP), in the presence and absence of roots, with and without mycorrhizae. Neutron imaging will be used to visualize and quantify root and mycorrhizal length density and morphology. The resulting data sets will be parameterized for inclusion in models used to predict flow and transport within the vadose zone. This work will address a key research uncertainty in our ability to adequately model plant-soil hydraulic relationships.
The goal of this research is to assess the impact of plant roots and mycorrhizal hyphae on soil hydraulic properties. The objectives are to measure the soil water retention curve, ?(?), and saturated hydraulic conductivity, ?sat in soil containing roots (with and without mycorrhizae) vs. no roots, and to visualize and quantify the spatial distributions of roots and hyphae. Based on a review of the literature, I hypothesize that roots and hyphae will change ?(?) by increasing the amount of water that is held at a given matric potential, particularly close to saturation. I also hypothesize that roots and hyphae will increase ?sat relative to soil in which they are absent.
- Elizabeth McNamee
Eilzabeth McNamee – University of Wisconsin
Quantifying the effectiveness of irrigation scheduling to increase water use efficiency in the WI Central Sands
Groundwater from a shallow, unconfined aquifer in the Wisconsin Central Sands (WCS) replenishes prized aquatic ecosystems and simultaneously supplies irrigation water to support a $450 million agricultural industry. To successfully balance these valuable ecosystem services, it is imperative we quantify the effectiveness of irrigation management strategies for reducing consumptive groundwater use while maintaining acceptable yields.
My proposed research will formally test the ability of the Wisconsin Irrigation Scheduling Program (WISP) – a tool available to farmers but severely underutilized – to increase crop water-use efficiency (WUE) and decrease consumptive groundwater use on-farm.
Potato and sweet corn crops will be examined across four fields during the 2018 and 2019 growing seasons. In a paired field experiment, half of the fields will be irrigated using the freely available WISP (https://wisp.cals.wisc.edu/), and Isherwood Farms will irrigate the remaining fields according to intuition and experience.
User inputs will be measured as follows: percent canopy cover with the Canopeo phone application, soil moisture with METER 5TM sensors/ProCheck, and irrigation/precipitation with METER ECRN-100. Previously installed METER G3 drain gauges (3-5 per field) and daily ET measurements (ET = rainfall + precipitation – Δ soil storage – drainage) will validate WISP deep drainage and ET calculations. One METER EM60G per field will log irrigation/precipitation (ECRN-100), soil moisture (10, 20, 40, 80 cm with 5TM; owned), and deep drainage (G3 drain gauge; owned) data. The EM60G’s automated data collection is vital for consistently tracking daily precipitation/irrigation inputs and accurately operating WISP. EM50s will collect data from additional lysimeters and soil moisture sensor sets (2-3 depending on the field) in order to capture a full range of variability. Yield will be determined by harvesting 6 meters of row from 15 field locations at the end of a crop growth cycle. Differences in deep drainage, yield, ET, and soil moisture will be compared between WISP-intuition irrigation regimes and WISP-Agro-IBIS models to evaluate potential water savings and opportunities for WISP improvement.