Models
Data Required
A variety of data are needed for model development and to constrain model calibration. Most of the required data is available; however, some pertinent data will need to be collected in order to fill gaps in available data and provide altitude control and stream-channel geometry.
Hydrogeology
- Existing hydrogeologic frameworks will be used to define hydrogeologic units with similar hydraulic properties and to inform and guide model parameter calibration.
- Middle HRB model will use the hydrogeologic framework described by
Plume and Ponce.
- Lower HRB model will rely on hydrogeologic frameworks developed by
Bredehoeft,
Cohen,
Prudic and Herman, and
Maurer and others.
Streamflow Data
- Will be obtained from the USGS
National Water Information system (NWIS).
- Long-term records are available for gages along the Humboldt River and some of the major tributaries.
- Data from the Carlin gage will be specified inflow to the middle HRB model for calibration and subsequent model scenarios.
- Data from the Comus gage will be specified inflow to the lower HRB model only for calibration.
- For scenario models, simulated stream outflow from the middle HRB model will be used as inflow to the lower HRB model.
- Data from other Humboldt River gages within the model domains will be used during the calibration process to help guide determination of hydraulic properties in both models.
Groundwater Levels
- Needed to adjust hydraulic properties of transmissivity and storage during calibration of the flow models.
- Long-term data is available throughout much of the developed areas of the Humboldt River Basin.
- Will be obtained from the USGS
NWIS database and the State of Nevada Division of Water Resources Water Level database.
- No new water-level measurements are planned as part of this project.
Evapotranspiration (ET) Discharge
- Estimates of ET discharge from riparian and phreatophytic areas are being developed for 1985–2015 by DRI.
- Will be used during model calibration to help constrain parameter estimates for the MODFLOW Evapotranspiration package and will help constrain simulated water budgets.
Water Budgets
- Existing water budget estimates for each hydrographic area within the model domains will be used to help constrain estimated model parameters during model calibration.
- Areas rich in hydrologic data and knowledge of aquifer properties may suggest revisions to existing water budget estimates are needed (such as groundwater recharge).
- Quality and/or reliability of existing data used in model calibration will be evaluated to make judgment on the reliability of existing water budget estimates.
- Water budget estimates will be allowed to deviate from existing estimates to improve model calibration, if hydrologic data and information are sufficient.
- Simulated water budgets for each hydrographic area will be compared with previous estimates and model suggested revisions will be reported.
Diversion Rates with Rights in Priority
- Streamflow-diversion rates for each of the major ranches of the Humboldt River are needed to simulate diversions from the Humboldt River.
- Diversion flow rates for the full distribution of priority rights on the Humboldt River have been reported in Hennen (1964b).
- Rights in priority are determined according to observed streamflow at the Palisade gage and existing lookup tables used by the Humboldt River Water Commissioners.
- Spatial datasets of irrigated lands associated with ranches served by diversions will be developed and used to guide determinations of where unused water is infiltrated.
Groundwater Withdrawals and Priority of Wells
- Data provided by the Nevada Division of Water Resources.
- Locations of all irrigation primary and supplemental wells, municipal wells, industrial wells, and aggregated domestic and stock water wells withdrawing more than 5 acre-feet per year will be used along with priority and withdrawal rates.
- Well location, depth interval of well screen, and priority dates will be compiled to ensure accurate location and simulation of groundwater stresses.
- Location of fields irrigated by supplemental wells and their ranch affiliation also will be used.
Pit Lakes
- Locations of pit lakes and relation of lake surface area and volume to lake depth are needed.
- Estimates of open water evaporation and precipitation rates and runoff contributionsalso are needed.
Geographic Information System (GIS) Geospatial Datasets
- GIS geospatial datasets will assist in the construction of the flow models.
- Most required datasets currently exist and are available.
- Datasets unavailable or not yet developed will be digitized from historic reports and maps.
- Expected geospatial datasets include Digital Elevation Model (DEM), National Hydrologic Dataset, agricultural lands subdivided by source of irrigation water (surface water, groundwater, or both), water-table contours and areas of shallow groundwater depicted in historic figures and plates.
Field work required to support model development
- Most of the information and data needed to develop and calibrate the flow models are available; some additional field data may be needed to achieve acceptable model accuracy.
- Simulation of groundwater and surface-water interactions requires relatively accurate estimates of groundwater-level altitudes and stream-level altitudes:
- Most streamflow gages in the Humboldt River Basin have an established datum within acceptable accuracy and do not require additional surveying.
- Some streamflow gages have datums determined from maps with high uncertainties and require more accurate determination.
- A survey grade GPS system will be used to determine altitudes of uncertain gage datum, stream-channel bottoms and cross sections.
- Cross sections will be collected at all existing streamflow-gage sites along the Humboldt River within the model domain, at tributary inflows, and at slope breaks in the Humboldt River stream profile.
- Separate Manning’s roughness coefficients will be assigned to both active (main channel) and inactive (flood plain) stream-channel cross sections and will be determined from existing streamflow measurements at streamflow gages, and through model calibration to match existing stage and discharge relations.
- Five aquifer tests will be conducted in the Lovelock area to improve aquifer property estimates used in the model.