|
|
Napa County Resource Conservation District |
|
| back |  RCD home |
|
|
Napa County Resource Conservation District |
|
| back | RCD home |
Introduction
Hydrology is a key technical area for the District. Since 1995 the RCD has had at least one full-time hydrology professional continuously on staff, and a number of staff members have been trained in hydrologic field work. We are working to develop basic hydrologic information for our District and to make analytical use of that information. Our work falls into two basic areas of activity: field hydrology and modeling.
The Importance of Hydrology
Briefly, hydrology is the science of water on earth. Since water is essential to human and other life, all natural resource conservation issues are in some way dependent on hydrology. The processes in nature that hydrology addresses are usually summarized using the idea of the hydrologic cycle, which includes evaporation of surface water, rainfall and snowfall, surface runoff and infiltration, and the exchange of water between streams and lakes - surface water - and groundwater storage.
Traditionally, hydrologists have been mainly concerned with water quantity, but water quality issues have in recent decades attracted more and more interest.
Field Hydrology
The District works with a network of volunteer monitors of water quantity and water quality. In addition to the volunteer monitoring network, the RCD has established professional streamgaging sites on selected tributaries of the Napa River watershed. These tributaries currently include Napa Creek, Salvador Creek, Milliken Creek, Huichica Creek, Carneros creek, and Murphy Creek. At the gaging sites, continuous measurements of water level are related to discharge by means of field discharge measurements, and suspended sediment measurements are taken as well. The gaging sites are maintained by our staff with the assistance of trained citizen volunteers (Flow Measurements).
The District has also collected cross-sectional information on streams in the Napa River system, through the efforts of our staff and citizen volunteers. The streams covered include the main stem of the Napa River from the City of Napa north to Kimball Dam, Huichica Creek, Hopper Creek, Garnett Creek, and Salvador Creek. In addition, citizen stewardship groups have collected information on other streams, with District assistance and training (Cross-sections)
Modeling
Since 1995 the Napa County RCD has maintained a dynamic unsteady flow model of the Napa River, which it is developing as a tool for integrated watershed management. The model is based on the MIKE 11 modeling software developed by the Danish Hydraulic Institute (DHI).
The model is an important element in the RCD's pursuit of its mission, which is to encourage and assist acceptance of individual responsibility for watershed management, using education and partnerships as the major tools for implementation of conservation goals. The RCD sees a computer model of the watershed as a whole as an important link between stewardship groups, helping them to see the watershed-wide consequences of resource management decisions they or others might make.
To date the model has been developed for the entire main stem of the Napa River and several tributaries. In addition to the main hydrodynamic module, a rainfall/runoff module has been developed as well (Modeling)
Flow Measurements
In our efforts to foster watershed stewardship, the District has always made much use of citizen volunteers, in the belief that the increased understanding and sense of investment in the watershed which result from volunteer activity will bring long-lasting benefits to all concerned. In the early 1990's the RCD initiated a program of volunteer monitoring of water quality and water quantity, which we continue to maintain.
Since 1995, we have supplemented this citizen monitoring with professional, staff-led streamgaging work. This has permitted us to deploy equipment for continuous measurements of water levels and to measure velocities using USGS-style current meters, while enjoying the benefits of local volunteer assistance. We are currently maintaining six stage/ discharge gaging stations on local creeks.
Our current policy is to dispatch teams of two or three individuals, one of whom is an RCD staff member thoroughly trained to supervise the measurement work. We are currently putting two or three such teams into the field during appropriate times in the wet season. For the small creeks we are measuring, it is not feasible to schedule field work more than a few hours in advance. Therefore, a staff member monitors rainfall daily (or oftener) through the wet season and schedules field work accordingly. Field work may fall on any weekday and occasionally falls on the weekend, but for safety reasons we avoid working after dark.
Our program, though relatively new, has been quite successful so far in providing useful information to the Napa River watershed community at a modest cost. The success of this program depends on training two sets of people:
- a core of trained professional staff who can make themselves available for streamgaging during winter storms
- a much larger group of volunteers, enough so that two or three can be mustered on short notice
Measurements of stream stage are currently being made using a combination of automated level monitoring equipment, installed and maintained by RCD staff, and ALERT system equipment installed and maintained by the City of Napa and Napa County. Currently we are using USGS-style current meters, in conjunction with either wading rods or sounding equipment, to measure velocities. Suspended sediment load is being sampled using isokinetic samplers.
For more information or to ask about specific sites or data, send an e-mail message to Paul Blank.
Cross-sections
The RCD has been measuring cross-sections of the channels in the Napa River system for several years. These measurements have been made in conjunction with the development of the MIKE 11 Napa River model, which the District initiated in 1995 in cooperation with Philip Williams & Associates.
RCD cross-section measurements are made by teams combining professional District and NRCS staff and trained citizen volunteers. The protocol used for cross-section measurements, along with other field protocols, appears in the Quality Assurance Project Plan for the Napa River Watershed Stewardship Project, CALFED project M92 (1998).
Cross-section data are in meters. Chainages are in meters, increasing in the downstream direction. For all cross-sectional surveys, the vertical datum is NGVD 29.
In 1995-96, a set of cross-sections of the main stem of the Napa River was carried out. The survey covered a stream length of 51 km, from Kimball Dam above Calistoga (chainage 000) to north Napa (Trancas Street bridge, chainage 51338), and it included 171 cross sections, of which 32 were supplied by other investigators. The maximum interval between cross sections was generally 400 m. The cross sections include the entire river channel and limited portions of the floodplain.
This Napa River survey, in conjunction with the cross-sections done for the Napa River flood protection project study and lower river soundings done for the Corps of Engineers, provided up-to-date complete coverage of the main stem of the Napa River.
A survey of the lower river in 1999 added 13 enhanced cross sections between the southern crossing bridge (chainage 62480) and the Edgerly Island tidal reference station (chainage 69760). These cross sections incorporate the most recent Corps of Engineers soundings of the navigation channel, with the addition of shoals, banks and levees.
In 1998 cross-sections of Garnett Creek and Hopper Creek were surveyed. In the case of Hopper Creek, the survey included Beard Ditch and the Yountville Outfall as well as portions of Dry Creek and Terry Slough. There are a total of 83 cross sections in this set, including 12 supplied by other investigators.
For more information about specific streams or data sets, send an e-mail message to Bob Zlomke.
Modeling
The RCD modeling effort began in 1995 with support from the California State Coastal Conservancy and other agencies, including the City of Napa and Napa County. This modeling effort is an aid in the RCD's ongoing pursuit of its mission, which is to encourage and assist acceptance of individual responsibility for watershed management. The RCD sees a computer model of the watershed as a whole as an important link between stewardship groups, helping them to see the watershed-wide consequences of resource management decisions they or others might make.
The Napa River Model is an unsteady flow hydraulic model based on the MIKE 11 Model developed by the Danish Hydraulic Institute (DHI). The MIKE 11 Model is an implicit finite difference model capable of modeling a network of one-dimensional channels, both for hydrodynamics and for a variety of water quality parameters. It is based on the St. Venant equations for one-dimensional unsteady flow, and as an unsteady flow model it is able to track the progress over time and space of floods, tidal events, and the interactions between the two, within the limits of a network of one-dimensional channels. These capabilities are particularly useful in the Napa River system, which is tidally influenced and experiences frequent flooding as well. In a similar fashion, specialized MIKE 11 modules can track the progress of a "wave" of concentration of sediment or other water quality constituent. These capabilities permit the study of a large variety of scenarios in which time plays a role.
In the first phase of development of the Napa River Model, a pilot study of hydrodynamics and salinity transport was carried out for the portion of the Napa River between Oak Knoll Avenue, just north of the city of Napa, and the Mare Island Causeway. This work was used as the foundation for further work on the Napa River flood protection project by Philip Williams & Associates (PWA), an environmental engineering consultant that collaborated with the District in initial development of the model.
Since that time, the model domain has been enlarged by the addition of a complete set of river cross sections from the previous upstream boundary at Oak Knoll Avenue to Kimball Reservoir, thanks to a strong volunteer effort and financial support from Napa County, so that the entire main stem of the river has been surveyed. The model was used to investigate potential improvements in flood conveyance that would result from the identification of constriction points upstream of the flood protection project. A separate model was developed for a site on Huichica Creek in southwest Napa County, where the effects of a floodplain restoration effort were to be studied.
More recently, the RCD has begun a program of adding tributaries to the model: under a grant from CALFED, Garnett and Hopper Creeks were added in 1999. Under the same grant, a rainfall/runoff model for the Napa River watershed was developed using the MIKE 11 rainfall/runoff module. A rainfall/runoff model was developed on the basis of eight years of rainfall and flow data, for the upper watershed (to Zinfandel Lane) and the central watershed (to Oak Knoll Avenue) separately; then the calibrated models were applied to the Garnett and Hopper subwatersheds and further calibrated on the basis of recent data.
To find out about current modeling projects, click here.
The following hydrology project reports are available:
- Haas, Julie. Napa River Watershed Hillside Development Runoff and Erosion Study. Napa County Resource Conservation District. 2000.
- Jones, Blaine K., and Robert Zlomke. Flood Modeling near Yountville: A Report Summarizing Flood Inundation Modeling with Various Levee Setback Alternatives. Napa County Resource Conservation District. 2001.
- Neary, Vincent, Peter Goodwin, Bob Zlomke, and Morten Rungø. Napa River Model: A Tool for Integrated Watershed Management, Phase I: Pilot Modeling and Concept Demonstration. Philip Williams & Associates, Ltd. 1996.
- Zlomke, Robert. Water Balance Study: A Component of the Watershed Management Plan for the Carneros Creek Watershed, Napa County, California.
- Zlomke, Robert, Julie Haas, and David Steiner. Modeling a Berm Setback on Huichica Creek. Napa County Resource Conservation District. 1998.
- Zlomke, Robert, and Blaine K. Jones. Hydrologic Modeling Assessment of the Lower Napa River. Napa County Resource Conservation District. 2001.
- Zlomke, Robert, and E. Woody Trihey. Napa River Flood Conveyance at Oak Knoll, A Model Demonstration. Napa County Resource Conservation District. 1998.
- Zlomke, Robert, Julie Haas and Jesper Kjelds. Adding Tributaries to the Napa River Model: A Report with Recommendations for a Program of Sediment Measurements in Tributaries. Napa County Resource Conservation District. 1999.
For more information about specific modeling projects, send an e-mail message to Paul Blank.
Current Projects
as of November 2004
(more a more recent list please contact our office)
- Streamgage Monitoring Program
With funding from the City of Napa, the California Regional Water Quality Control Board, and Vintage Grapevine, Inc., the RCD maintains water level measuring equipment and performs streamgaging and suspended sediment sampling at select sites on several Napa River tributaries.
- Hydrologic Modeling in the City of Napa
With funding from the City of Napa, the RCD is carrying out a project to complete and maintain MIKE 11 hydrologic models of Napa Creek and Salvador Creek.
- Sediment and Stewardship Project
With funding from the California Regional Water Quality Control Board, the RCD maintains suspended sediment monitoring stations on Carneros Creek, and in the York Creek watershed, to evaluate potential changes in sediment delivery to the Napa River drainage system as a result of land use changes and practices, particularly vineyard development and design.
- Witweather Creek Project
With funding from Napa County Flood Control and Water Conservation District, the RCD is investigating drainage related problems that occur during the rainy season in an area along Witweather Creek in Coombsville.
Streamgage Monitoring Program
With funding from the City of Napa, the California Regional Water Quality Control Board, and Vintage Grapevine, Inc., owner of Consentino Winery, the RCD:
- Maintains automated water level measuring and recording stations to measure stream water levels on four Napa River tributaries;
- Performs streamgaging during the rainy season at six established gaging stations on Napa River tributaries; and,
- Collects water samples at the gaging stations during streamgaging visits for analysis of suspended sediment concentration.
The RCD maintains automated water level measuring and recording stations on Salvador Creek, Huichica Creek, Carneros Creek, and Murphy Creek. The stations include telemetric systems that allow interested parties to obtain instantaneous water level data by telephone, and provide the RCD with continuous water level records at these sites.
During the rainy season, the RCD performs streamgaging at six sites on Napa River tributaries: the four creeks listed above as well as Napa Creek and Milliken Creek. During streamgaging, RCD staff measure water depth and velocity to calculate water discharge during storms. The data are used to develop a rating curve for the stream for use in flood monitoring and modeling, water use planning, and evaluation of fish passage and protection.
During streamgaging at each site, the RCD collects water samples from the stream for analysis of suspended sediment concentration (SSC) using USGS-approved equipment and the equal transit rate method. SSC data are used to develop sediment load – stream discharge rating curves for use in a variety of purposes including water quality and fish habitat studies.
For more information, send an e-mail message to Paul Blank.
back to "Current Projects" index
or
top of page
Hydrologic Modeling in the City of Napa
Under a contract with the City of Napa, the RCD is updating previously-developed MIKE 11 hydrologic models of Napa Creek and Salvador Creek using rainfall and stream discharge data collected during the 2003-2004 water year. On Napa Creek, the results will be used to compare existing conditions to proposed flood project improvements. The Salvador Creek model will be used to evaluate restoration scenarios developed by the Salvador Creek stewardship group.
For more information, send an e-mail message to Bob Zlomke.
back to "Current Projects" index
or
top of page
Sediment and Stewardship Project
With funding from the California Regional Water Quality Control Board, the RCD studies sediment delivery to the Napa River drainage system by rainfall runoff. The RCD has established two project areas: the vineyard runoff sites in the York Creek watershed and stream sediment monitoring stations on Carneros Creek.
The vineyard runoff sites are two adjacent vineyard blocks of approximately 0.5 acres each at a ranch near St. Helena. The two are similar in soil, slope and aspect but differ in drainage design and management of ground cover. One site is an older-style vineyard block with no piped drainage and annual tillage, while the other site is a more modern vineyard block with piped drainage and a no-till regime. Direct runoff from each is measured by means of flumes and datalogging equipment, and samples of runoff are collected for analysis of suspended sediment concentration.
The RCD has established two stream sediment stations on Carneros Creek for continuous measurement of stage and turbidity and for turbidity-threshold sampling of suspended sediment concentration.
The sediment and stewardship project began in the Spring of 2002 and is scheduled to continue through the Spring of 2005. The results of the project, which will be presented in a final report due by June 2005, are expected to provide valuable data on sediment delivery into our streams.
For more information, send an e-mail message to Paul Blank.
back to "Current Projects" index
or
top of page
Witweather Creek Project
With funding from Napa County Flood Control and Water Conservation District, the RCD is investigating drainage related problems that occur during the rainy season in an area along Witweather Creek in Coombsville. In order to identify the factors contributing to the drainage problem, the RCD is examining the creek’s surrounding watershed, measuring all channel culverts, bridge openings, and a number of channel cross-sections throughout the watershed, and evaluating the capacity of each culvert, bridge opening, and channel to transport large flows. Upon completion, the RCD will prepare a Storm Drain Master Plan for submittal to Napa County that identifies problem areas.
For more information, send an e-mail message to Chad Edwards.
|
|
RCD home |
|
| back |