Source: UTAH STATE UNIVERSITY submitted to
PROCESSES OF SURFACE HYDROLOGY IN THE SEMI-ARID WEST
Sponsoring Institution
State Agricultural Experiment Station
Project Status
TERMINATED
Funding Source
STATE
Reporting Frequency
Annual
Accession No.
0191409
Grant No.
(N/A)
Project No.
UTA00361
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2001
Project End Date
Jun 30, 2007
Grant Year
(N/A)
Project Director
Chandler, D. G.
Recipient Organization
UTAH STATE UNIVERSITY
(N/A)
LOGAN,UT 84322
Performing Department
Plants, Soils & Climate
Non Technical Summary
Winter and springtime water quality and flooding are controlled by the interplay between the hydrologic processes which predominate during the winter and early spring, yet these processes remain poorly understood for the semi-arid West. The project is intended to identify the predominant hydrologic mechanisms operating in the semi-arid West, particularly under cold season and snowmelt conditions.
Animal Health Component
(N/A)
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
11203992050100%
Knowledge Area
112 - Watershed Protection and Management;

Subject Of Investigation
0399 - Watersheds and river basins, general;

Field Of Science
2050 - Hydrology;
Goals / Objectives
Identify the temporal and spatial variability of hydrologic pathways, particularly lateral subsurface flow in semi-arid landscapes of the Intermountain West. Initial work in the Cache valley will focus on selecting representative canyon and valley bottom sites. The canyon site will be a zero order (ephemeral stream) basin with a steep slope and shallow soils. It should be similar to an ongoing research near Boise, Idaho, to allow comparison of results. The valley bottom site(s) will be chosen to represent the impact of land-use changes and management strategies on the hydrology of the urban-rural fringe. The objective of this project will be met by testing the following hypotheses. Hypothesis 1. When snow cover is persistent, the soil remains unfrozen and all precipitation infiltrates until the soil surface is saturated, after which overland flow will occur if the precipitation (or snow melt) rate exceeds the infiltration rate. Hypothesis 2. When frozen soil is present, more overland flow will occur prior to saturation, but the relative magnitude of overland flow will depend on the moisture content of the near surface soils at the time of freezing. Hypothesis 3. Infiltrated water will move laterally downslope as unsaturated flow and can be explained by a decline in unsaturated hydraulic conductivity with soil depth due to a persistent decline in moisture content and increase in soil bulk density. Hypothesis 4. Near the base of the slope, lateral flow in the upper portion of the soil column will be dominated by new water, whereas the lower portion of a soil column will be fed by old water from the regolith.
Project Methods
Experiments will be conducted at the hill slope and plot scale, where flow into the reservoirs and conduits along the hydrologic cycle will be quantified by state of the art techniques. Precipitation includes rain and snow melt, with snow melt being the primary source of water for infiltration. It is therefore important to measure both additions to and releases from the water reservoir held in the snow pack. Rain and snowfall will be measured by a weighing bucket gage with a wind shield mounted on a post approximately 1.5 m above the ground surface. Snow depth will be monitored hourly by a sonic depth sensor. Weekly snow surveys will be performed to obtain snow water equivalent. Knowledge of the soil water content and frost status prior to and during high infiltration flux is critical to understanding hydrologic pathways. Volumetric soil moisture content will be monitored by time domain reflectometry in soil pits arranged along a hill slope transect. Thermocouples will record soil temperature as a proxy for frost depth at the same depths as the moisture content sensors. Soil pore water pressure (pressure and tension) will be measured at equivalent locations by pressure transducers with a hydraulic connection to porous ceramic cups. Output from all sensors will be logged hourly to datalogger. A telemetry system will be added to each site to facilitate data acquisition and timely soil water sample collection. A hill slope-scale conservative tracer (KBr) study will test the hypothesis of the predominant hydrologic mechanism at each site. Suction and zero-tension lysimeters will be installed along three transects extending from the channel to the crest of the hill. The lysimeters will be installed to the depth of the lithic contact, or to 1 m. Where the depth to the lithic contact is greater than 50 cm, an additional lysimeter will be installed to a depth of 30 cm. Hydraulic conductivity will be measured at each lysimeter borehole by Guelph permeameter. A line source of KBr will be applied across the slope. Periodic sampling of the suction lysimeters and any collected surface runoff will be analyzed for Br- concentration.

Progress 07/01/01 to 06/30/07

Outputs
The project proposed to test four hypotheses: 1) When snow cover is persistent, the soil remains unfrozen and all precipitation infiltrates until the soil surface is saturated, after which overland flow will occur if the precipitation (or snowmelt) rate exceeds the infiltration rate. This hypothesis was reframed based on the findings that field soils in sloping topography seldom if ever exceed field saturation, which may be as little as one half the moisture content at pore-filled saturation. Runoff events were associated with transient and widespread near surface soil moisture contents above field saturation. 2) When frozen soil is present, more overland flow will occur prior to saturation, but the relative magnitude of overland flow will depend on the moisture content of the near surface soils at the time of freezing. We did not collect sufficient data to test this hypothesis. 3) Infiltrated water will move laterally down slope as unsaturated flow and can be explained by a decline in unsaturated hydraulic conductivity with soil depth due to a persistent decline in moisture content and increase in soil bulk density. This hypothesis is supported by field data, but is complicated at the hill slope scale by variability in soil depth, which can introduce dry soil pockets as barriers to lateral flow. 4) Near the base of the slope, lateral flow in the upper portion of the soil column will be dominated by new water, whereas the lower portion of a soil column will be fed by old water from the regolith. Most runoff at the catchment scale was found to be derived from water which precipitated in the same water year. This result clarifies that for semi-arid environments, all ephemeral and most intermittent stream flow is essentially new water.

Impacts
Improved measurement methods and new hydrologic theory developed through this project will contribute to the next generation of hydrologic models. These models will provide more precise estimates of annual water yield, especially under changing climate and for hydrologic extremes.

Publications

  • Chandler, DG, M Seyfried, M Murdock and J McNamara. 2004. Field calibration of water content reflectometers. Soil Science Society of America Journal 68:1501-1507.
  • Kelleners, TJ, MS Seyfried, JM Blonquist, Jr., J Bilskie, DG Chandler. 2005. Permittivity measurements in air, fluids, and soils using Water Content Reflectometers. Soil Science Society of America Journal 69:1684-1690.
  • Chandler, DG, M Seyfried. 2005. Response to comments on field calibration of Water Content Reflectometers. Soil Science Society of America Journal 69:1357-1358.
  • McNamara, J, D Chandler, S Achet, M Seyfried. 2005 Soil moisture states, lateral flow, and streamflow generation in a semi-arid, snowmelt-driven catchment. Hydrological Processes 19:4023-4038.


Progress 01/01/05 to 12/31/05

Outputs
Significant progress has been achieved in the conceptual framework of the hydrology of Dry Creek relative to the core hypotheses in the original proposal. These may be revised as follows: Hypothesis 1. When snow cover is persistent, the soil remains unfrozen and all precipitation infiltrates. In general, the slopes are adequately steep to maintain near free drainage conditions and the soils do not saturate except near the soil bedrock interface. Overland flow is uncommon and transient. Hypothesis 2. Most runoff is generated from an isothermal snowpack during warm spring conditions. Frozen soil is seldom a large consideration for coarse textured soils or in areas overlain by a persistent winter snowpack. Hypothesis 3. Infiltrated water will move laterally downslope as unsaturated flow and can be explained by a decline in unsaturated hydraulic conductivity with soil depth due to an increase in gravel and rock fragment and soil bulk density. Hypothesis 4. Near the base of the slope, lateral flow in the upper portion of the soil column will be dominated by new water, whereas the lower portion of a soil column will be fed by old water from the soil matrix. The ratio of the old water to new water in any streamflow hydrograph depends on the spatial extent and duration of hillslope to stream connection, which can be related to the distributed antecedent soil moisture and mass flux of water inputs during the event. The impacts of increased precipitation and temperature were tested independently in SHAW model exercises at two elevations in Dry Creek. The results concur with observations throughout the western US that warming temperatures will be associated with earlier spring runoff and lower annual flows. However the extent to which bedrock infiltration will change in a changing climate is not clear. These updated hypotheses are being tested through a distributed hydrologic model built for semi arid snowmelt conditions. Data sets for future model testing are being compiled for supplemental research locations in Utah and Vermont.

Impacts
As the population of the western US has grown, so has the need for better prediction of hydrologic extremes, both for flood warnings and water supply management. Ongoing field research has targeted the interplay between vegetation controls, disturbance regime and patterns of infiltration for headwater snowmelt areas and basin rangelands. Field and modeling experiments indicate that spring weather in mountain source areas will determine the extent of flooding in high snowfall years and drought severity in low snowfall years. Incorporating these findings into hydrologic forecast models is expected to improve the precision with which water managers can forecast water yields.

Publications

  • Ritu Gupta, MS Thesis, Civil and Environmental Engineering, Utah State University. 2005 Investigation of elevation-related controls on semiarid mountain front hydrology by modeling of water balance.
  • Ajay Kalra, MS Thesis, Civil and Environmental Engineering, Utah State University. 2005 Vertical and lateral flow components of soil water fluxes following spring rainfall in a semiarid catchment.
  • Kelleners, TJ, MS Seyfried, JM Blonquist, Jr., J Bilskie, DG Chandler. 2005. Improved interpretation of Water Content Reflectometer measurements in soils. Soil Science Society of America Journal 69: 1684-1690.
  • Chandler, DG, M Seyfried. 2005. Response to Comments on field calibration of Water Content Reflectometers. Soil Science Society of America Journal. 69:1357-1358.


Progress 01/01/04 to 12/31/04

Outputs
Data analysis and research product development has continued for the Dry Creek Watershed project. The current research emphasis is identification and quantification of the temporal and spatial distribution of infiltration, lateral flow and hydraulic connectivity within the focus study site. Adequate information has been obtained to develop a conceptual framework for additional model testing and development at the larger watershed scale. Further research will be conducted under CRIS Project UTA00372. The research methods developed at the Dry Creek site have been implemented at three additional sites to test the effect of soils, climate and vegetation on the surface hydrology. At the Upper Sheep Creek Watershed background data for assessing the hillslope-level plant and edaphic controls on hydrologic response has been collected with collaborators from the USDA ARS. These data are being used to frame upcoming research on fire impact on mountain source area hydrology in the Great Basin. At TW Daniel Experimental Forest, research has been initiated to assess the temporal variability of soil moisture storage under aspen, sage, conifers and grasses. Further research for these projects will be conducted under CRIS Project UTA00372. Similar experiments have been implemented at Sleepers River Experimental Watershed collaboratively with the USGS to test climatic controls over hillslope response. Field research on the interplay between vegetation controls, disturbance regime and patterns of infiltration has continued on the Colorado Plateau. Further research to extend this work to various disturbance regimes is currently supported by the Bureau of Land Management.

Impacts
As the population of the western US has grown, so has the need for better prediction of hydrologic extremes, both for flood warnings and water supply management. Ongoing field research has targeted the interplay between vegetation controls, disturbance regime and patterns of infiltration for headwater snowmelt areas and basin rangelands. Field and modeling experiments indicate that spring weather in mountain source areas will determine the extent of flooding in high snowfall years and drought severity in low snowfall years. Incorporating these findings into hydrologic forecast models is expected to improve the precision with which water managers can forecast water yields.

Publications

  • McNamara, J, D Chandler, S Achet, and M Seyfried. 2005. Evidence for the timing of hillslope-stream connectivity from water budget calculations. Hydrological Processes in press.
  • Chandler, DG, M Seyfried and J McNamara. 2004. Field calibration of water content reflectometers. Soil Science Society of America Journal, 68:1501-1507.


Progress 01/01/03 to 12/31/03

Outputs
An existing research site in the Dry Creek Experimental Watershed, near Boise, ID has been extensively instrumented with Time Domain Reflectometry waveguides to determine soil moisture content and tensiometers to determine soil water potential. Analysis of the first year of data show considerable promise for the experimental approach, which allows not only the development of in-situ soil water release curves for representative locations throughout the hillslope, but also evidence of hydrologic response behavior that diverges from the near steady state assumptions of such curves generated under laboratory conditions. The degree and timing of hydraulic connectivity within each slope of the catchment is documented in the data set from 2003 for rain on snow, snowmelt and rainfall conditions. Continued modeling efforts validated the application of the SHAW model for this system. Unfortunately, the snowmelt and rain on snow events were very small compared to previous years. The experiment will be conducted for an additional year to investigate the snowmelt response for a larger snowpack. Continued modeling efforts validated the application of the SHAW model for this system.

Impacts
Translation of water through the soil of hillslopes to the stream network is a highly non-linear process, yet it has often been greatly simplified in hydrologic models. Understanding the predominant mechnaisms by whichh water translates through the soil under different input conditions, such as snowmelt, rain and rain on snow will enhance our ability to predict the amount and timing of streamflow generated in mountainous headwaters under both drought and flood conditions.

Publications

  • No publications reported this period


Progress 01/01/02 to 12/31/02

Outputs
Comparison of model output and field results indicate that considerable variability exist in the hydraulic connection between hillslope and stream in semi-arid landscapes, yet the current modeling approaches are inadequate to fully explain the field measurements. An existing research site in the Dry Creek Experimental Watershed, near Boise, ID has been extensively instrumented with Time Domain Reflectometry waveguides to determine soil moisture content and tensiometers to determine soil water potential. The intent of the experiment is to determine the degree and timing of hydraulic connectivity between two hillslopes of different aspects and the ephemeral stream draining the research site.

Impacts
The expected impact of this resaerch is an improved understanding of the hillslope scale controls on streamflow generation. The expected application of the results is improvement of continuous hydrologic modeling approaches.

Publications

  • No publications reported this period