..Title Receive Report on Salinas Valley Water Conditions for the Third Quarter of Water Year

Transcription

1 ..Title Receive Report on Salinas Valley Water Conditions for the Third Quarter of Water Year Report RECOMMENDATION: It is recommended that the Monterey County Water Resources Agency Board of Directors: Receive report on Salinas Valley water conditions for the third quarter of Water Year SUMMARY/DISCUSSION: This report covers the third quarter of Water Year (WY17), April, 2017 through June, It provides a brief overview of water conditions in the Salinas Valley (Attachment A) with discussion of precipitation, reservoir storage, and ground water level trends. Data for each of these components are included as graphs and tables in Attachments B through J. Precipitation The third quarter of WY17 brought below normal rainfall to Salinas and King City. Cumulative totals for the quarter were 0.93 inches (68% of normal rainfall of 1.37 inches for the quarter) at the Salinas Airport, and 0.70 inches (61% of normal rainfall of 1.14 inches for the quarter) in King City. Attachment B contains graphs for both stations showing monthly and cumulative precipitation data for the current and a normal water year. Attachment B also includes tables showing values for precipitation totals as well as percent of normal precipitation. Rainfall data for Salinas and King City should be considered preliminary until verified by National Weather Service data at a later date. Reservoirs - The following table compares third quarter storage at Nacimiento and San Antonio reservoirs for WR17 and WR16. Storage in Nacimiento Reservoir is 159,890 acre-feet higher than in June 2016, and storage in San Antonio Reservoir is 147,165 acre-feet higher. Reservoir June 30, 2017 (WY17) Storage in acre-feet June 30, 2016 (WY16) Storage in acre-feet Difference in acre-feet Nacimiento 276, , ,890 San Antonio 170,955 23, ,165 Graphs for both reservoirs showing daily storage for the last five water years along with periodof-record daily average storage for comparison are included as Attachments C and D. Groundwater Levels More than 80 wells are measured monthly throughout the Salinas Valley to monitor seasonal groundwater level fluctuations. Data from approximately 50 of these wells are used in the preparation of this report. The measurements are categorized by hydrologic

2 subarea, averaged, and graphed to compare current water levels with selected past conditions. Graphs for individual subareas, showing the current year s water level conditions, last year s conditions (WY16), dry conditions (WY91), and near-normal conditions (WY85), are found in Attachments E through I. Groundwater level measurements indicate that water levels continued to recover in all subareas through the month of April. In May and June water levels began their seasonal decline in the Pressure 180-Foot Aquifer, the Pressure 400-Foot Aquifer and the East Side Subarea, while hovering at seasonal high levels in both the Forebay and Upper Valley Subareas. Attachment J is a summary of water level changes for all subareas. From May to June, average groundwater levels were unchanged in the Forebay and Upper Valley Subareas while declining by three feet in the Pressure 180-Foot Aquifer, two feet in the Pressure 400-Foot Aquifer and ten feet in the East Side Subarea. Compared to June 2016, average June 2017 groundwater levels rose by seven feet in the Pressure 180-Foot Aquifer, six feet in the Pressure 400-Foot Aquifer, five feet in the East Side Subarea, fourteen feet in the Forebay Subarea, and ten feet in the Upper Valley Subarea. When compared to WY85, which is considered to be a year of near normal groundwater conditions, June 2017 water levels were eight feet lower in the Pressure 180-Foot Aquifer, one foot lower in the Pressure 400-Foot Aquifer, twenty-nine feet lower in the East Side, one foot lower in the Forebay Subarea and six feet lower in the Upper Valley Subarea. Average WY17 groundwater levels ended the third quarter slightly above WY91 (dry condition) levels in the Upper Valley Subarea, while exceeding WY91 water levels by six feet in the Forebay Subarea, three feet in the Pressure 180-Foot Aquifer and eleven feet in the P400-Foot Aquifer. In the East Side Subarea, water levels remained five feet below WY91 water levels. OTHER AGENCY INVOLVEMENT: None FINANCING: From Water Resources Agency Funds 114, 115, 116 Prepared by: Howard Franklin, Senior Hydrologist, (831) Peter Kwiek, Hydrologist, (831) Sean Noble, Water Resources Technician, (831) Approved by: David E. Chardavoyne, General Manager, (831) Attachments:

3 1. Attachment A, Salinas Valley Hydrologic Subareas Map 2. Attachment B, Salinas and King City Precipitation Graphs 3. Attachment C, Nacimiento Reservoir Graph 4. Attachment D, San Antonio Graph 5. Attachment E, Groundwater Trends Pressure 180-Foot Aquifer 6. Attachment F, Groundwater Trends Pressure 400-Foot Aquifer 7. Attachment G, Groundwater Trends East Side Subarea 8. Attachment H, Groundwater Trends Forebay Subarea 9. Attachment I, Groundwater Trends Upper Valley Subarea 10. Attachment J, Groundwater Trends Summary

4 EAST SIDE SALINAS VALLEY GROUNDWATER BASIN HYDROLOGIC SUBAREAS SALINAS MARINA ZONE 2C Third Quarter of Water Year CHUALAR GONZALES PRESSURE 0 L SA SOLEDAD Miles AS IN EL ER IV R ER IV R M AR C GREENFIELD FOREBAY KING CITY SAN LUCAS PACIFIC OCEAN SAN ARDO UPPER VALLEY BRADLEY SAN ANTONIO RESERVOIR MONTEREY COUNTY SAN LUIS OBISPO COUNTY ATTACHMENT A NACIMIENTO RESERVOIR

5 Rainfall (inches) Rainfall (inches) 18 SALINAS AIRPORT RAINFALL WATER YEAR 2017 Legend Normal WY (Monthly Avg) WY 2017 (Monthly Total) 10 Normal WY (Cumulative Total) WY 2017 (Cumulative Total) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Monthly Rainfall (WY 2017) Monthly Rainfall (Normal WY*) Percent of Normal for Month 329% 107% 78% 225% 178% 54% 90% 6% 78% Cumulative Rainfall (WY 2017) Cumulative Rainfall (Normal WY*) Percent of Cumulative Normal 329% 172% 126% 165% 169% 146% 142% 138% 137% 18 KING CITY RAINFALL WATER YEAR 2017 Legend Normal WY (Monthly Avg) WY 2017 (Monthly Total) Normal WY (Cumulative Total) 8 6 WY 2017 (Cumulative Total) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Monthly Rainfall (WY 2017) Monthly Rainfall (Normal WY*) Percent of Normal for Month 149% 68% 64% 308% 174% 45% 77% 19% 80% Cumulative Rainfall (WY 2017) Cumulative Rainfall (Normal WY*) Percent of Cumulative Normal 149% 98% 80% 168% 169% 144% 140% 136% 136% *Average precipitation over the most recent 30-year period ending in a decade ( ) ATTACHMENT B

6 400,000 NACIMIENTO RESERVOIR DAILY STORAGE 350, ,000 Spillway = 377,900 acre-ft. Elev. = 800 ft. Daily Average ( ) June 30, 2017 Storage = 276,980 acre-ft. Elev. = ft. Water Storage in Acre-Feet 250, , , ,000 ATTACHMENT C 50,000 0 Jul-12 Oct-12 Jan-13 Apr-13 Jul-13 Oct-13 Min. Pool = 22,300 acre-ft. Elev. = ft. Jan-14 Apr-14 Jul-14 Oct-14 Jan-15 Date Apr-15 Jul-15 Oct-15 Jan-16 Apr-16 Jul-16 Oct-16 Jan-17 Apr-17 Jul-17

7 SAN ANTONIO RESERVOIR DAILY STORAGE 350, ,000 Spillway = 335,000 acre-ft. Elev. = 780 ft. Water Storage in Acre-Feet 250, , ,000 Daily Average ( ) June 30, 2017 Storage = 170,955 acre-ft. Elev. = ft. 100,000 ATTACHMENT D 50,000 0 Jul-12 Oct-12 Jan-13 Apr-13 Jul-13 Oct-13 Jan-14 Min. Pool = 23,000 acre-ft. Elev. = 666 ft. Apr-14 Jul-14 Oct-14 Date Jan-15 Apr-15 Jul-15 Oct-15 Jan-16 Apr-16 Jul-16 Oct-16 Jan-17 Apr-17 Jul-17

8 GROUNDWATER TRENDS PRESSURE 180-FOOT AQUIFER 5 Wells Average Depth to Water, in feet OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month 1985 WY 1991 WY 2016 WY 2017 WY ATTACHMENT E

9 GROUNDWATER TRENDS PRESSURE 400-FOOT AQUIFER 11 Wells Average Depth to Water, in feet OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month 1985 WY 1991 WY 2016 WY 2017 WY ATTACHMENT F

10 GROUNDWATER TRENDS EAST SIDE SUBAREA 11 Wells Average Depth to Water, in feet OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month 1985 WY 1991 WY 2016 WY 2017 WY ATTACHMENT G

11 GROUNDWATER TRENDS FOREBAY SUBAREA 10 Wells Average Depth to Water, in feet OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month 1985 WY 1991 WY 2016 WY 2017 WY ATTACHMENT H

12 GROUNDWATER TRENDS UPPER VALLEY SUBAREA 9 Wells Average Depth to Water, in feet OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month 1985 WY 1991 WY 2016 WY 2017 WY ATTACHMENT I

13 Groundwater Trends Summary June 2017 Area June 2017 Depth to Water 1 Year Change Change From WY Month Change Pressure 180-Foot Aquifer 56' up 7' down 8' down 3' Pressure 400-Foot Aquifer 49' up 6' down 1' down 2' East Side Subarea 153' up 5' down 29' down 10' Forebay Subarea 70' up 14' down 1' no change Upper Valley Subarea 52' up 10' down 6' no change June water levels, compared to last year, range from 5' higher to 14' higher. June water levels, compared to WY 1985, range from 29' lower to 1' lower. June changes in water levels over the last month range from 10' lower to no change. ATTACHMENT J