Executive Summary

Recognition of Problem
The desire to achieve integrated resources management in the Willow Slough watershed reflects an awareness of natural resource problems and a spirit of cooperation and innovation among local residents. Many residents are keenly aware of changes in resource conditions that have gradually occurred over a number of decades: 

1. Flooding problems seem to be worse;
2. Wildlife populations have declined; 
3.  Erosion and sedimentation are damaging structures and depleting topsoil; 
4.  The county needs additional water supplies; 
5. Maintaining flood conveyance capacity in slough channels is a significnant on-going expense.

Although these resources and problems have traditionally been managed separately, a few local agencies and individuals began to recognize that multiple benefits might be achieved by managing them together. For example, detaining stormwater in numerous small ponds could decrease downstream flood peaks, create seasonal or perennial wetland habitat, trap sediment, and recharge groundwater through percolation from the ponds.

A Planning Process
A planning process was initiated by the Yolo County Resource Conservation District, Yolo County Flood Control and Water Conservation District, Yolo County Community Development Agency, and the California Wildlife Conservation Board to explore the possibilities for managing natural resources throughout the watershed in an integrated manner. This two-year process involved the participation of numerous landowners; federal, state, and local agencies; and the general public, culminating in the development of this plan document. Technical support was provided by Jones & Stokes Associates, the Yolo County Community Development Agency, and Borcalli & Associates.

Planning Goal
The goal of this plan is to enhance the natural resources of Yolo County through integrated management of natural resources on individual farms and throughout the watershed using voluntary, small-scale measures that can be implemented by individual landowners. The resources and problems that could be jointly managed include stormwater, erosion, sedimentation, agriculture, wildlife habitat, and groundwater recharge.

Getting Started
The first step in the planning process was to systematically inventory natural resources and resource problems in the watershed. After defining the boundaries of the 164-square-mile study area,maps and tables were developed to characterize precipitation, land forms,soils, crops, stream flow, flooding patterns, groundwater levels, water supply, and existing and potential habitat. Digital maps were prepared using a geographic information system. An existing HEC-1 model of the watershed was used to characterize flood hydrology and hydraulics.

Resource Evaluation
The resource inventory revealed that the watershed is basically in good condition but has several resource management problems. Flooding disrupts traffic on rural roads and causes damage to fields and crops on a fairly frequent basis. Erosion is evident in the hilly western part of the watershed, along channels, and in fields in the relatively flat eastern part of the watershed. Sediment generated by the erosion is deposited along fields, roads, and waterways, where it creates safety hazards, increases overbank flooding along sloughs, and interferes with agricultural activities. There is much less riparian and wetland habitat in the watershed than under predevelopment conditions, and wildlife populations that depend on these habitats are declining.

Opportunities
The resource inventory provided the basis for exploring opportunities to achieve multiple benefits by managing resources in an integrated manner. This analysis focused on opportunities for creating or enhancing wetland and riparian habitats, augmenting groundwater recharge, and decreasing flooding problems.

Evaluation Methods
The geographic information system was used to develop maps of suitability for habitat and groundwater recharge by quantitative screening of relevant factors, such as soil characteristics, slope, existing crop type, flooding patterns, habitat, and groundwater levels.The watershed was divided into five general areas reflecting differences in terrain, soils, hydrology, and land use: the upper watershed area, foothills area, valley floor area, Plainfield Ridge, and drainage channels.

Observations
This process revealed large areas where physical conditions are suitable for creating or restoring wetlands. Suitability for establishment of riparian habitat is limited to narrow bands along sloughs and canals, but there is substantial opportunity to increase the length, width, and continuity of riparian habitat in the watershed. Opportunities for generating large amounts of groundwater recharge by detaining floodwater and allowing it to percolate are somewhat limited by the generally low permeability of most soils in the valley floor area. However, gradual percolation distributed over a large area is the principal source of recharge under existing conditions, and ponds or impoundments of any size that increase the area or prolong the duration of percolation would augment groundwater supplies.

Evaluation Models
The HEC-1 model was used to evaluate opportunities for decreasing peak flood flows. The effects of constructing numerous small stock ponds, habitat ponds, and tailwater ponds were simulated using reasonable assumptions regarding the number and size of ponds that might eventually be constructed. The combined amount of flood storage capacity provided under these assumptions proved to be too small to substantially decrease peak flood flows in slough channels in the valley floor area. Larger reservoirs or more aggressive implementation of ponds would be needed to decrease flows by detaining stormwater runoff. The effects of clearing vegetation from slough channels and enlarging slough channels were also simulated. These strategies had a larger effect on peak flood flows. The simulations demonstrated that if channels are enlarged, riparian vegetation can be allowed to provide habitat benefits in the channel while still achieving a net increase in flood conveyance capacity.

Constraints
Constraints on achieving habitat, flood control, and groundwater recharge benefits were also evaluated. Opportunities for creating and enhancing habitat are abundant, and interested landowners could implement successful projects almost anywhere in the watershed. The feasibility of flood control is generally limited by the large amounts of runoff generated during storms. The terrain and hydrology of the watershed are conducive to frequent and widespread flooding in the valley floor area; flooding was common even under predevelopment conditions. To a certain extent, flooding is inevitable, and the best strategy would be to direct floodwater to areas where it creates the fewest impacts on transportation, structures, and agriculture.

Developed Strategies
The screening analysis of opportunities and constraints confirmed that integrated resources management strategies can have multiple and mutually beneficial effects. For example, detaining stormwater in ponds or on fields can support seasonal or perennial wetland habitat, improve water quality by trapping sediment, and increase groundwater recharge. The best strategies for integrating management of natural resources are not the same throughout the watershed, and a map was developed showing the most advantageous strategies for the various areas in the watershed.

Specific Implementation Measures Effects on Resources
Measures to improve habitat or flood problems involve land use changes that could potentially affect other resources. For example, seasonal or permanent conversion of cropland to wetlands or riparian areas could adversely affect farm budgets or the countywide agricultural economy. Wetlands could also become a source of mosquitoes. Various potential impacts on other resources were evaluated at a general level and were found to be beneficial (recreation, aesthetics, and education) or very minor (economics, mosquitoes, and water supply).

Current Activities
A few landowners have already implemented some of the measures described in the plan, and the planning process generated considerable additional interest. There are also some measures that have not been tested or that have poorly documented effectiveness. For these reasons, several pilot projects were identified and described at a conceptual design level to illustrate how the planning concepts and implementation measures can be applied at specific sites and to assist landowners in winning support for their efforts to improve resource management.

Impact of Regulations
The number and complexity of regulations that potentially apply to the types of resource management activities recommended in this plan can be bewildering and inhibit many landowners from taking action. To clarify the regulatory environment, concise descriptions of the applicability and requirements of the major regulatory programs are included in this plan. Fortunately, most of the measures recommended would generally benefit the resources the regulations are designed to protect. Agencies exercise discretion in applying regulations and would probably look favorably on projects that include the implementation measures described in this plan. There is also interest among some agencies in streamlining the permitting process to facilitate improved resources management. Two approaches to simplifying and streamlining the permitting process for landowners are presented in the plan.

Available Programs
The plan also includes a catalog of 25 federal,state, and private programs that provide financial or technical support for natural resources management projects. It is clear that integrated resources management on a watershed scale is a widely supported concept. One of the most encouraging results of the planning process was the recognition that all of the key ingredients needed to move forward with improved resources management are in place: willing landowners, sources of funding, and sources of technical assistance. To be successful, the plan needs only to serve as a catalyst to bring these ingredients together and empower local residents to achieve their vision of a healthy, beautiful, and productive watershed.

This integrated resource management plan was prepared in May of 1996. Several groups in Yolo County, California, were involved.

Prepared for: 

•  Yolo County Resource Conservation District
• California Wildlife Conservation Board
• Yolo County Flood Control and Water Conservation District
• Yolo County

Prepared by:

• Jones & Stokes Associates, Inc.
• Yolo County Community Development Agency