truckee river watershed ??these include bear creek, squaw creek, donner creek, trout creek, little...

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  • Water Quality Assessment and Modeling of the California Portion of the Truckee River Basin David McGraw Alan McKay Guohong Duan Thomas Bullard Tim Minor Jason Kuchnicki

    JULY 2001

    Publication No. 41170

    Prepared by Division of Hydrologic Sciences, Desert Research Institute, University and Community College System of Nevada, Las Vegas Prepared for: Town of Truckee

    Lahontan Regional Water Quality Control Board

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    EXECUTIVE SUMMARY

    The purpose of this study is to provide the technical analysis and review necessary to begin developing a Total Maximum Daily Load (TMDL) for sediment for the California portions of the Truckee River watershed. The general goal of a sediment TMDL analysis is to protect designated uses by characterizing existing and desired watershed conditions, evaluate the degree of impairment to the existing (and future) conditions, and identify land management and restoration actions needed to attain desired conditions (USEPA, 1999a). More specifically, the goals of this study are: 1) establish recommended reductions in sediment loads for designated reaches and sub-basins in the upper basin of the Truckee River; 2) develop a GIS-based watershed model capable of simulating erosional and sediment transport processes over multiple physiographic settings; 3) use the calibrated model to estimate sediment conditions under various land-use scenarios; and 4) interact with technical advisory groups to ensure stakeholder input from project inception through completion.

    The water column indicator was chosen for this study because of the availability and quantity of data available as well as relative ease of collection over streambed sediment indicator data. Targets were determined using a watershed model to estimate the effect on sediment load from an assumed, undisturbed condition. The calibrated model was used to simulate increased canopy cover and removal of dirt roads, two parameters responsible for much of the sediment production in the basin. The intent of an increase in canopy cover is to simulate recovery of areas that experience a removal of vegetation resulting from some anthropogenic disturbance. Similarly, dirt roads are a disturbance that can be removed in the model. A comparison of model results from the calibrated, present condition to the target condition suggests a 47% reduction in sediment load is required in the Truckee River Basin to achieve the target.

    The analysis and review includes creating an evaluation of general sources of sediment in the basin. This is accomplished in two ways: 1) collection and synthesis of sediment and flow records for the main stem of and tributaries to the Truckee, and 2) development of a watershed model to estimate sediment loadings under various land uses.

    Using historic data, annual sediment load was estimated for ten major tributaries to the Truckee River. These include Bear Creek, Squaw Creek, Donner Creek, Trout Creek, Little Truckee River, Prosser Creek, Juniper Creek, Gray Creek, and Bronco Creek. Loads were estimated for the 1996 and 1997 calendar years.

    To assess the watershed in greater detail, a watershed model capable of estimating sediment load was created. The model was calibrated to 1996 data and validated to 1997 data. Results from the modeling exercise show the relative magnitude of areas that contribute sediment to the Truckee River. In general, two conclusions can be made: 1) areas closer to the river affect in-stream sediment concentrations greater than those a greater distance from the river, and 2) areas at higher elevations (typically found with steep slopes) produce high sediment per unit area.

    Additionally, sensitive landscapes are identified to assist land managers and planners in their decisions to add or modify land-use practices. The aerial photo analysis was performed to complement the previous two assessments and identified areas of erosion vulnerability (or

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    sensitivity) in the basin. Erosion vulnerability was determined primarily by the relative degree of soil development, or soil age. Aerial photos of the basin at scales ranging from 1:15,000 to 1:30,000 were used to identify geologic units. A detailed analysis was performed in Martis, Gray, and Bronco creeks. A coarser, basin-wide analysis was performed using the Landsat image from August 1999.

    As preparation for the Implementation requirement of the final TMDL, an evaluation of relevant best management practices (BMPs) was performed in this study. Because of the inconsistency in scale between BMPs and the model, BMP effectiveness was evaluated in a general sense using the model. The change in sediment load resulting from revegetation, removal/redesign of dirt roads, and decreased application rate of road sand was quantified using the model. Significant reduction in suspended sediment load can be achieved by each of the three BMPs analyzed in this study. In addition, it is clear that BMPs are more effective when implemented in areas closer to the stream.

    Included in this report is a review of existing monitoring and recommendations for future monitoring plan development. An ancillary benefit to collecting all relevant historic data and developing a model is a thorough understanding of data needs, data gaps, and potential high-sediment-producing areas. In the monitoring plan, areas of concern are identified and a discussion of monitoring techniques, advantages, and disadvantages is provided.

    The format of this report follows the suggested outline in Protocol for Developing Sediment TMDLs (USEPA, 1999a).

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    CONTENTS EXECUTIVE SUMMARY....................................................................................................ii LIST OF FIGURES.................................................................................................................vii LIST OF TABLES .................................................................................................................viii 1. PROBLEM STATEMENT..........................................................................................1

    1.1 Introduction.................................................................................................................1 1.2 Surface Water Quality Objectives Violated and Standards Not Attained...................1 1.3 The Truckee River Watershed.....................................................................................1

    1.3.1 Climate................................................................................................................... 2 1.3.2 Geology ................................................................................................................. 2 1.3.3 Soils ....................................................................................................................... 3 1.3.4 Vegetation .............................................................................................................. 6 1.3.5 Streamflow ............................................................................................................. 6

    1.4 Beneficial Uses............................................................................................................7 1.5 Impairment of Beneficial Uses by Increased Sediment ..............................................7

    2. WATER QUALITY INDICATORS AND POSSIBLE NUMERIC TARGETS ....8 2.1 Background .................................................................................................................8

    2.1.1 Entrainment and Transport....................................................................................... 8 2.1.2 Sediment Sources.................................................................................................... 9

    2.2 Indicators ...................................................................................................................10 2.2.1 Water Column Indicators....................................................................................... 10 2.2.2 Streambed Sediment Indicators .............................................................................. 12

    2.3 Target Values ............................................................................................................13 2.3.1 Overview.............................................................................................................. 13 2.3.2 Current Study ....................................................................................................... 14

    3. SOURCE ANALYSIS ................................................................................................15 3.1 Objective ...................................................................................................................15 3.2 Data Description........................................................................................................16

    3.2.1 Spatial Data .......................................................................................................... 16 3.2.1.1 Spatial Database Construction ......................................................................... 16 3.2.1.2 Input for AnnAGNPS Model and Subsequent Analysis of Model Results........... 18 3.2.1.3 Scale, Accuracy and Reliability....................................................................... 20

    3.2.2 Suspended Sediment Loading ................................................................................ 24 3.2.2.1 Historic Data.................................................................................................. 24

    3.2.2.1.1 Suspended Sediment Data: USGS ................................................................24 3.2.2.1.2 Suspended Sediment Data: Desert Research Institute .

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