Salinity Management: Salinity Management: Status of Regional - - PDF document

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Salinity Management: Salinity Management: Status of Regional - - PDF document

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Salinity Management: Salinity Management: Status of Regional Status of Regional Water Basins Water Basins The Wake- The Wake -up Call up Call Prior to 2002 there were no TDS related Prior to 2002 there were no TDS related

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Salinity Management: Salinity Management: Status of Regional Status of Regional Water Basins Water Basins

The Wake The Wake-

  • up Call

up Call

  • Prior to 2002 there were no TDS related

Prior to 2002 there were no TDS related impairments on the 303(d) List impairments on the 303(d) List

  • In 2002 11 waterbodies were added to the

In 2002 11 waterbodies were added to the 303(d) list for TDS related impairments 303(d) list for TDS related impairments

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San Diego Regional 303(d) San Diego Regional 303(d) Workgroup Workgroup

  • Formed in reaction to the 2002 303(d)

Formed in reaction to the 2002 303(d) listing process as a workgroup of Project listing process as a workgroup of Project Clean Water Science and Technology Clean Water Science and Technology Technical Advisory Committee Technical Advisory Committee

  • Prepared an Analysis of Total Dissolved

Prepared an Analysis of Total Dissolved Solids in San Diego County and submitted Solids in San Diego County and submitted to SWRCB as part of the 2002 303(d) to SWRCB as part of the 2002 303(d) listing process listing process

Basin Planning Issues Workgroup Basin Planning Issues Workgroup

  • Formed in 2003 to discuss the triennial

Formed in 2003 to discuss the triennial review of the San Diego Basin Plan review of the San Diego Basin Plan

  • Total Dissolved Solids Management Plan

Total Dissolved Solids Management Plan and the Development of Water Quality and the Development of Water Quality Objectives for Nutrients identified as Objectives for Nutrients identified as priority issues by stakeholders and priority issues by stakeholders and submitted as part of the triennial review submitted as part of the triennial review process process

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More Recently More Recently

  • In 2006, another 27 waterbodies were

In 2006, another 27 waterbodies were added to the 303(d) list for TDS related added to the 303(d) list for TDS related impairments impairments

  • How many more will be added in the 2008

How many more will be added in the 2008 update of the 303(d) list? update of the 303(d) list?

Water Quality Standard for TDS Water Quality Standard for TDS in Surface Waters in Surface Waters

  • Established in 1975 when Basin Plan was

Established in 1975 when Basin Plan was adopted. adopted.

  • WQS = 500 mg/L applied to most

WQS = 500 mg/L applied to most subbasins within the San Diego Region. subbasins within the San Diego Region.

  • Protective of Municipal Drinking Water

Protective of Municipal Drinking Water and Agricultural Supply Beneficial Uses. and Agricultural Supply Beneficial Uses.

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Total Dissolved Solids include: Total Dissolved Solids include:

Carbonates/bicarbonates Carbonates/bicarbonates Chlorides Chlorides Sulfates Sulfates Phosphates Phosphates Nitrates Nitrates Magnesium Magnesium Sodium Sodium Iron and Iron and Manganese Manganese

Rationale for Surface Water WQS Rationale for Surface Water WQS for TDS, Sulfate, Chloride, for TDS, Sulfate, Chloride, Manganese and Iron Manganese and Iron

  • Prevent taste problems in potable water

Prevent taste problems in potable water supplies supplies

  • Prevent leaf burn and salinity

Prevent leaf burn and salinity-

  • related crop

related crop reductions reductions

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Groundwater Water Quality Groundwater Water Quality Objectives Objectives

  • In most cases exceed surface WQOs

In most cases exceed surface WQOs

  • Not subject to the Federal Clean Water

Not subject to the Federal Clean Water Act, therefore much easier to change Act, therefore much easier to change

TDS Concentrations in Stormwater TDS Concentrations in Stormwater

Data from the Regional Stormwater Monitoring Program Wet Weather Mass Loading Stations

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Estimated TDS Concentration Estimated TDS Concentration in Dry Season Flows in Dry Season Flows

600 600 380 380 -

  • 1040

1040 Tijuana Tijuana 2175 2175 700 700 -

  • 3775

3775 Sweetwater Sweetwater 1350 1350 665 665 -

  • 1845

1845 San Diego San Diego 2380 2380 525 525 -

  • 5020

5020 San Dieguito San Dieguito 2410 2410 905 905 -

  • 6665

6665 Carlsbad Carlsbad 1395 1395 952 952 -

  • 1945

1945 San Luis Rey San Luis Rey 965 965 795 795 -

  • 1175

1175 Santa Margarita Santa Margarita

Average Average (mg/L) (mg/L) Observed Observed Range (mg/L) Range (mg/L) Watershed Watershed

2007 Data measured as conductivity and converted to TDS

TDS in Groundwater TDS in Groundwater

500 500 -

  • 3000

3000 Tijuana Tijuana 300 300 -

  • 3100

3100 Sweetwater Sweetwater 1000 1000 -

  • 3000

3000 San Diego San Diego 1000 1000 -

  • 1500

1500 San Dieguito San Dieguito 500 500 -

  • 3400

3400 San Luis Rey San Luis Rey 600 600 -

  • 1500

1500 Santa Margarita Santa Margarita

Observed Observed Concentrations (mg/L) Concentrations (mg/L) Watershed Watershed

Data from San Diego County Water Authority Groundwater Report , June 1997

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The Influence of Groundwater on The Influence of Groundwater on Surface Waters Surface Waters

  • Alluvial valleys contain unconfined

Alluvial valleys contain unconfined groundwater groundwater

  • Considerable interchange between surface

Considerable interchange between surface flow and groundwater flow flow and groundwater flow

  • Incompatibility between ground and surface

Incompatibility between ground and surface water quality objectives in Basin Plan water quality objectives in Basin Plan

Influence of Surface Water Influence of Surface Water Hydrology Hydrology

1300 1300 0 -

  • 10

10 960 960 10 10 -

  • 20

20 800 800 20 20 -

  • 50

50 610 610 50 50 – – 100 100 420 420 > 100 > 100 Mean Streamflow Mean Streamflow TDS Concentration TDS Concentration (mg/L) (mg/L) San Diego River San Diego River Streamflow Streamflow (CFS) (CFS)

  • Direct relationship between the magnitude if

Direct relationship between the magnitude if surface flow and mineral concentrations surface flow and mineral concentrations

  • When flows are low, poor

When flows are low, poor-

  • quality surfacing

quality surfacing groundwater dominates. groundwater dominates.

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Influence of Imported Water on Dry Influence of Imported Water on Dry Season Streamflow Season Streamflow

0.0 0.0 0.3 0.3 0.0 0.0 15.7 15.7 1930 1930 -

  • 1967

1967 Observed Flow (CFS) Observed Flow (CFS) 1968 1968 -

  • 2000

2000 4.4 4.4 Median Monthly Flow: June Median Monthly Flow: June – – Oct. Oct. 14.2 14.2 Mean Flow: June Mean Flow: June – –Oct. Oct. 10.2 10.2 Median Monthly Flow Median Monthly Flow 56.5 56.5 Mean Annual Flow Mean Annual Flow Parameter Parameter

When significant imported water deliveries began When significant imported water deliveries began there was a measurable increase in dry season flows there was a measurable increase in dry season flows

San Luis Rey River at Oceanside

Imported Water Impacts Imported Water Impacts

  • In 2005, 89.9% of water supply imported

In 2005, 89.9% of water supply imported (573,048 acre (573,048 acre-

  • feet)

feet)

  • Largest source of salt imported into San

Largest source of salt imported into San Diego Watershed Diego Watershed

  • Directly affects the salinity of recycled

Directly affects the salinity of recycled water water

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Hodges Reservoir, February 2005

Reservoirs in the San Diego Region

  • 24 reservoirs, total storage

capacity 571,000 acre feet

  • Most located in rural east County

areas, but, increasingly at risk from residential and commercial development

  • San Diego’s reservoirs are part of

the state-wide water supply system

  • watershed management = source

water protection

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City of San Diego Water Department

Local Source Water System

Hodges San Vicente El Capitan Cottonwood Otay

Sutherland

San

Miramar Murray

Diego

Total Watershed Area 926 sq miles

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$ $ $

Local Sources 15-20% ~30% of total supply from local reservoirs Imported Sources 80-85%

Salinity in Drinking Water

TDS, chloride, sulfate are secondary standards in drinking water

  • affects taste, odor, appearance
  • not a health effect at regulated levels

500 250 sulfate 500 250 chloride 1000 500 TDS

upper (mg/L) recommended (mg/L) constituent

Taste, odor, appearance are the #1 complaint / inquiry from water customers

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Salinity in San Diego’s Drinking Water Sources

  • Imported sources

–Colorado River ~ 700 mg/L –State Project ~ 300 mg/L –MWDSC blends sources to deliver water at <500 mg/L to San Diego

  • Local surface runoff impounded in

reservoirs ~150 to 400 mg/L

Basin Plan Standards and “Impairment” of Reservoirs

  • TDS Water Quality Objective at

reservoirs

– most reservoirs 500 mg/L – San Vicente & El Capitan 300 mg/L

  • 303(d) listing of reservoirs

– 2002 Hodges – 2006 San Vicente, El Capitan, Murray, Miramar

  • “If you monitor, they will be listed.”
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Basin Plan Standards and “Impairment” of Reservoirs

  • TDS listing of reservoirs dropped from

final 2006 list (State Board overrode staff recommendations)

Management of Salinity vs San Diego’s drinking water sources: a Paradox

  • local water agencies strive to deliver

water of <500 mg/L

  • imported water +/- 500 mg/L
  • local reservoirs store imported water,

but are influenced by local runoff

  • Where to focus efforts to manage

salinity in drinking water reservoirs?