Basics
Suspended Sediment Load (Surface Runoff)
Suspended Sediment Load in Runoff
Intermediate Result
Program
Kilogram (kg)
No
1. Reduce total annual nutrient and suspended sediment loads as necessary to achieve loading thresholds for tributaries and littoral and pelagic Lake Tahoe.
2. Tributaries - Reduce total annual nutrient and suspended sediment load to achieve loading thresholds for littoral and pelagic Lake Tahoe.
3. Littoral - Decrease sediment load as required to attain turbidity values not to exceed three nephelometric turbidity units (NTU). In addition, turbidity shall not exceed one NTU in shallow waters of the lake not directly influenced by stream discharges.
4. Deep Water (Pelagic) Lake Tahoe – Reduce fine sediment particles (inorganic particle size less than 16 micrometers in diameter), total phosphorus, and total nitrogen in order to achieve the following long-term water quality standards for deep water (pelagic zone) Lake Tahoe:
a) The annual average deep water transparency as measured by Secchi disk shall not be decreased below 29.7 meters (97.4 feet), the average levels recorded between 1967 and 1971 by the University of California, Davis.
b) Maintain annual mean phytoplankton primary productivity at or below 52gmC/m2/yr.
Kilograms/year of fine sediment particles.
This Indicator is reported in the following LT Info areas:
Status

No Subcategories for this Indicator.

Program Regional Stormwater Monitoring

Approach

Monitoring is guided by the RSWMP Framework and Implementation Guidance document. During water year 2014 five catchments were monitored for continuous flow and turbidity and sampled for water quality at eleven monitoring stations: the outfalls of the five selected catchments, and the inflows to and outflows from selected BMPs located in three of those catchments. Three additional catchment outfalls were monitored in water year 2015. The catchments were chosen because of their direct hydrologic connectivity to Lake Tahoe, diversity of urban land uses, range of sizes, and a reasonably equitable distribution among the participating jurisdictions. BMP effectiveness sites were selected because of their potential efficacy in treating storm water runoff characteristic of the Lake Tahoe Basin, and the broad interest in, and lack of conclusive data regarding the efficiency of the selected BMPs in reducing runoff volumes and pollutant loads.

Partners

Associated Programs data not provided.

Suspended Sediment Load (Surface Runoff) is include in the Threshold Dashboard. Threshold Indicators are evaluated against Threshold Standards every 4 years. Thresholds are environmental goals and standards for the Lake Tahoe Basin that indirectly define the capacity of the Region to accommodate additional land development.

2011 Evaluation

Status
Insufficient Data to Determine Status or No Target Established
Trend
Insufficient Data to Determine Trend
Confidence
Low

2015 Evaluation

Status
Insufficient Data to Determine Status or No Target Established
Trend
Insufficient Data to Determine Trend
Confidence
Low

2019 Evaluation

The 2019 Threshold Indicator evaluation is not available yet. Check back soon for updates.
Key Messages
About the Threshold
Water Quality
Surface Runoff
This indicator measures the total suspended sediment load (measured as fine sediment particle load) delivered to Lake Tahoe via direct surface runoff. Fine suspended sediment (fine sediment particles) are the primary driver of the decline in lake clarity (responsible for 55 to 60 percent of the decline) and urban upland areas are the dominate source of fine sediment particle in the basin (Lahontan and NDEP, 2010a). The TMDL estimated that 72 percent of the fine sediment particle load originates from urban sources. The TMDL estimated that a 71 percent reduction (from 2004 loading estimate) in fine sediment particle load from urban upland sources over 65 years would be required to achieve the pelagic clarity standard.
Landscape modification (e.g. impervious cover such as roads or residential and commercial development or logging) influences the volume of runoff, erosion rates, and the ability of the watershed to retain sediment and nutrients. Sediment and nutrient load in stormwater runoff is influenced by the type, magnitude, and location of landscape modifications and the extent to which practices to mitigate potential impacts are in place. A variety of natural factors also influence the load of sediment and nutrients in stormwater including climate, weather, landscape topography, and vegetation. The TMDL estimated that 72 percent of total fine sediment particle load basin wide originates from urban upland sources.
Standards
Management with Numeric
Reduce total annual nutrient and suspended sediment loads as necessary to achieve loading thresholds for tributaries and littoral and pelagic Lake Tahoe.
Reduce loads of fine sediment particles, total nitrogen, and total phosphorus as established by Lake Tahoe TMDL