AGENDA ITEM C9 TAMPA WATER

Transcription

1 TAMPA WATER Supplying Water To The Region AGENDA ITEM C9 DATE: June 3, 28 TO: Gerald J. Seeber, General Manager FROM: Donald J. Polmann, Director of Science and Engineering SUBJECT: Regional Water Supply and Current Drought Status - Status Report SUMMARY: Tampa Bay Water remains under Level II Water Shortage hydrologic conditions as the spring dry season continues. Regional demands increased in response to below normal rainfall and rising temperatures. Surface water supplies continued to decline due to less than normal May rains; reliance on storage in the Regional Reservoir and desalination production continues. Circumstances remain such that demand management actions are continuously encouraged for the community at large and specifically for the Member Governments. RECOMMENDATION: Receive status report. DISCUSSION: While regional water demands significantly increased starting mid-april as rainfall declined and temperatures rose, total regional water demands (Figure 1) and Tampa Bay Water deliveries (Figure 2) for the month of May 28 are below the rates experienced in water years 26 and 27. Total regional demands for May are down nine million gallons per day (mgd) from the two previous years. Tampa Bay Water's lower deliveries result from the lessened regional demand and also less sale of water to the City of Tampa (due to its self-reliance on the Hillsborough River source). The direct regional benefit is a reduction in historic springtime groundwater pumpage from regional wellfields; the twelve month running average production from the regional wellfields continues to drop. Surface water supplies declined during May resulting from below-normal rainfall. Reliance on storage in the C. W. Bill Young Regional Reservoir and on desalination facility production continues. This Agenda Item details the current hydrologic conditions relating to surface water supply sources and presents a water supply strategy for the remainder of Water Year 28 which targets the 12-month running average compliance goal for the Consolidated Permit Wellfields (9 mgd) by the end of September 28 (Figure 3). Current Supply Conditions At least 5 mgd of water from the C.W. Bill Young Regional Reservoir has been drawn of late in order to achieve the required water elevation of 17 feet or lower to complete testing of the drain system (see Agenda Item C-1 in this Board Agenda Packet) and T:\Sci_Eng _Board\28\Jun8\Regional Water Supply and Current Drought Status.doc

2 Gerald J. Seeber June 3, 28 Page 2 installation of additional monitoring equipment at elevation 1 feet. As of May 31, 28 the reservoir stage was 1.6 feet (5.2 billion gallons stored in the Regional Reservoir - Figure 4). Surface water treatment plant production averaged 59.3 mgd for the month of May and production is targeted to average 6 mgd or greater for the remainder of the water year. Storage is adequate to continue meeting demands through the remainder of this dry season and beyond. The Tampa Bay Seawater Desalination plant averaged mgd and mgd during the months of April and May, respectively, and is targeted to average 25 mgd during the months of June through July and to average at least 2 mgd for August and September. Production from the 11 Consolidated Wellfields has been reduced; May 28 production averaged mgd (compared to May 27 production average of mgd). Tampa Bay Water will continue monitoring production from the 11 Consolidated Wellfields in relation to the new limit of 9 mgd which has an effective regulatory compliance date of December 31, 28. For the month of May 28, groundwater production from the 13 Tampa Bay Water wellfields totaled mgd and surface water (including desalinated water and water purchased from the City of Tampa) totaled mgd. Current Hydrologic Conditions While rainfall totals for the months of February through April were above normal, the region has seen very little rainfall since the first week in April. Conditions during the past six weeks have been typical of the region's spring dry season. Rainfall totals for both the Hillsborough River and Alafia River watersheds are slightly below normal for the October 27 through May 28 time period. More significant is the fact that a prolonged rainfall deficit remains for these two watersheds, as illustrated on Figure 5. Surface water flows rebounded in April; however, flows began declining toward the end of April and remain below long-term means expected for this time of year. Figures 6 and 7 provide a comparison of long-term expected monthly flows to actual river flows in the Hillsborough River and Alafia River watersheds for Water Years 26, 27 and 28 (through May 28). In both watersheds, river flow has been below expected rates for nearly two years. The mean monthly flow in the Hillsborough River at the Morris Bridge gauge for May 28 was 35 mgd and the mean monthly flow in the Alafia River at the Lithia gauge was 27 mgd. These mean monthly streamflows were 54% and 33% of longterm monthly average flows, respectively. Flow in the Hillsborough River at the Morris Bridge gauge (the farthest downstream flow gauge on the river prior to the City of Tampa reservoir) is used to characterize the degree to which the current streamflow has exceeded or fallen short of historic normal levels over die previous 12 months. A flow deficit or surplus is determined for the previous 12 months and the median of these values is recorded. The sign and magnitude of the median value indicates the persistence of flows above normal (positive medians) or flows below normal (negative medians). The current 12-month median deficit flow at the Hillsborough River Morris Bridge gauge is mgd; flow conditions during the past 6 days have improved slighdy. T:\Sci_Eng _Board\28\Jun8\Regional Water Supply and Current Drought Status.doc

3 Gerald J. Seeber June 3, 28 Page 3 Storage in the City of Tampa's Hillsborough River reservoir was full at the start of the spring dry season. With declining surface water flow over the past six weeks, storage has depleted; the Harney Augmentation Pump Station was activated on May 8, 28 and has since provided 474 million gallons to the City's reservoir. The City initiated its request for regional potable water on May 3, 28, and is expected to need 1-2 mgd until the summer rains begin. Drought Mitigation Plan Actions The stage in the Regional Reservoir has reached 1 feet as of May 31, 28. This condition, in combination with a median streamflow deficit of greater than 1 mgd (current flow deficit is over 36 mgd), indicates that Tampa Bay Water and its member governments continue under a regional water supply shortage. The Level II Water Supply Shortage requires the following demand management actions: Member Governments continue one day per week watering restrictions. Active and increased enforcement of water restrictions by all Member Governments. Continue public communications program. The program goal is to increase public awareness of drought conditions and help mitigate outdoor water demand. Tampa Bay Water initiated an umbrella program for the region, with Member Governments using and promoting components of the program where appropriate. Member Governments are requested to continue public conservation messaging and to maintain or increase water restriction enforcement across the region consistent with drought mitigation management strategies. BACKGROUND: Since December 21, the region has operated under the Boardapproved Drought Mitigation Plan (DMP) that provides specific triggers, demand management actions, and operational actions. The existing Board-approved DMP is implemented based on current rainfall-deficit conditions and the regional drought index using data available at the beginning of each month. Potential enhancements that should be explored by the Member Governments during declared water shortage periods include comparing water use restriction enforcement by day-of-week versus demand (there appears to be elevated demand on non-watering days), evaluating changes in water use for new development areas that are permitted under new higher water-use efficiency ordinances, and determining if specific messaging/enforcement is affecting outdoor water uses. Staff continues to work with Member Governments in collecting water restriction and conservation information, discussing and exploring various short-term and long-term demand management alternatives, implementing a consistent public awareness campaign throughout the region, and identifying additional opportunities to optimize existing water resources. Attachments T:\Sci_Eng _Board\28\Jun8\Regional Water Supply and Current Drought Status.doc

4 Figure 1. Comparison of Tampa Bay Regional Demands for Water Years 26, 27 and MGD Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept WY 26 WY 27 WY 28

5 Figure 2. Comparison of Tampa Bay Water Deliveries for Water Years 26, 27 and MGD Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept WY 26 WY 27 WY 28

6 Figure 3. Consolidated Wellfield 28 Actual and Projected Production and 12 Month Running Average MGD 8 MGD Oct-7 Nov-7 Dec-7 Jan-8 Feb-8 Mar-8 Apr-8 May-8 Jun-8 Jul-8 Aug-8 Sep-8 Actual Wellfield Production Projected Wellfield Production 12 Month Running Average

7 8 7 Figure 4. C.W. Bill Young Regional Reservoir October BG Monthly Divers sions (Billions of Gal lons) July BG July BG Nov BG Storage Vo olume (Billions of Gallons) O- 5 N- 5 D- 5 6 F- 6 M- A- M A- 6 S- 6 O- 6 N- 6 D- 6 7 F- 7 Month Reservoir Influent Reservoir Effluent Cumulative storage M- 7 A- 7 M A- 7 S- 7 O- 7 N- 7 D- 7 8 F- 8 M- 8 A- 8 M- 8-4 T:\Sci_Eng _Board\28\Jun8\Regional Water Supply Fig 4.xlsFigure 12

8 Figure 5. Cumulative Rainfall Deficit for St. Leo and Plant City Rain Gauges 5-5 Inch hes inches inches Alafia River Watershed Hillsborough River Watershed

9 Figure 6. Hillsborough River Monthly Mean Flow at Morris Bridge Gage Data through 5/31/ WY 26 WY 27 WY 28 MGD Longterm Mean Flows WY 26-28

10 6 Figure 7. Alafia River Monthly Mean Flow at Lithia Gage Data through 5/31/ MGD 3 WY 26 WY 27 WY Longterm Mean Flows WY 26-28