Tampa Bay Water Drought Mitigation Plan

Transcription

1 Tampa Bay Water Drought Mitigation Plan December 2001

2 Tampa Bay Water Drought Mitigation Plan December 2001

3 Executive Summary Purpose The purpose of the drought mitigation plan (DMP) is to identify and simplify specific actions that will be taken during periods of hydrologic drought and corresponding water supply shortfalls. The plan outlines when various levels of water supply shortage occur and identifies the actions to be taken. This plan differs from historical water shortage approaches used by the Southwest Florida Water Management District (SWFWMD) by including hydrologic triggers associated with specific demand management and supply augmentation actions. This approach aids in communication and credibility with the public through consistent and defined triggers and actions. As new water supply sources are brought online and operational experience with the enhanced surface water system (ESWS) increases, the DMP will need to be recalibrated. The plan is designed to allow triggers and actions to be modified as needed. Triggers and Actions Table ES-1 summarizes the recommended triggers and actions. The plan is designed for water supply conditions beginning in January 2003, when production from the Consolidated Permit wellfields is reduced to the regulatory limit of 121 million gallons per day (mgd) and all System Configuration I supplies except the regional reservoir are online. However, the rainfall-deficit-based triggers and demand management and supply augmentation actions can be implemented at any time following Board approval of the plan. Rainfall-deficit based triggers were established by a detailed analysis of historical rainfall and corresponding river flows in the tri-county region. A 12-month rolling cumulative rainfall (RCRF) deficit was selected to lessen the effects of seasonal rainfall variations. The analysis showed a significant reduction in surface water flows of the Hillsborough River and Alafia River when the regional RCRF deficit exceeded 10 inches. The 10-inch deficit level was selected as the initial trigger of the DMP and defined as Level I (drought alert). As shown in Table ES-1, two other levels of drought were defined: Level II (water shortage), and Level III (water supply crisis). These levels are directly linked to supply availability during hydrologically-stressed periods. Actions corresponding to each drought level are also shown in Table ES-1. Reservoir-based triggers were established by a detailed analysis of the proposed ESWS. Historical RCRF deficits were compared to ESWS flows and allowable withdrawals to simulate reservoir conditions under varying hydrologic conditions. Reservoir-based triggers were then selected corresponding to reservoir stages for 90 and 30 days of remaining supply. At 90 days of remaining supply (Level II water shortage) the DMP recommends activating the Morris Bridge Sink as the supply augmentation action. With 30 days of supply remaining (Level III water crisis) the DMP recommends temporary use of the groundwater resource and existing infrastructure to avoid construction of costly new supplies, which TPA/W:/W155797/DMP FINAL REPORT1_ DOC DECEMBER 6, 2001 iii

4 would only be needed during very infrequent conditions. Based on the hydrologic period ( ) used in this analysis, a Level III water crisis has occurred once. The recommended DMP includes rainfall-based and reservoir-based triggers, demand management actions, and supply augmentation. A proactive plan such as this will provide Tampa Bay Water with an operational tool to meet its water supply obligations in times of water supply shortages due to hydrologic drought conditions. TABLE ES-1 Drought Mitigation Plan: Triggers and Actions Drought Levels On Triggers Off Demand Management Actions Supply Augmentation I. Drought Alert RCRF Deficit 10 RCRF Deficit 5 Initiate public messaging and Increase effectiveness of 2 day per week lawn watering restrictions (e.g., enforcement) II. Water Shortage 6 month average RCRF Deficit 10 or RCRF Deficit 10 or 1 day per week lawn watering restrictions Morris Bridge Sink On: Approximately 15 mgd Reservoir Elev. < 102 (90 days of supply) Reservoir Elev. > 109 (120 days of supply) III. Water Supply Crisis At Water shortage for 12 months or Reservoir Elev. < 87 (30 days of supply) 6 month average RCRF Deficit 10 or Reservoir Elev. > 102 (90 days of supply) Members implement options for measurable demand reduction Optimize all supplies to meet demand, including temporary exceedance of Consolidated Wellfields Permit Note: RCRF = 12 month rolling cumulative rainfall deficit TPA/W:/W155797/DMP FINAL REPORT1_ DOC iv

5 Contents Section Page Executive Summary...iii Purpose of a Drought Mitigation Plan Background and Introduction Project Objectives Drought Management Plan Technical Advisory Committee (DMP TAC) Project Approach Phase I Drought Mitigation Plan Development Phase I Triggers Conceptual Phase I Drought Mitigation Process and Plan Phase I Conclusions Phase II Drought Mitigation Plan Development Data Analysis Conclusion Impacts on Supply Development of Recommended Triggers Supply Augmentation Options Demand Management Actions Communications Strategy Drought Mitigation Process and Plan Appendix A List of Figures Number Page 1 Phase I - Relationship Between Level of Drought and Possible Mitigation Actions Tampa Bay Water Supply Capacities Beginning January Drought Mitigation Decision Process List of Tables Number Page ES-1 Drought Mitigation Plan: Triggers and Actions...iv 1 Conceptual Drought Mitigation Plan Drought Mitigation Plan: Recommended Triggers Summary of Historical Rainfall-Based Drought Triggers Key Drought Messages and Delivery Methods Drought Mitigation Plan: Triggers and Actions TPA/W:/W155797/DMP FINAL REPORT1_ DOC v

6 Purpose of a Drought Mitigation Plan The purpose of this drought mitigation plan (DMP) is to identify and simplify specific actions that will be taken during periods of hydrologic drought and corresponding water supply shortfalls. The plan outlines when various levels of water supply shortage occur and identifies the actions to be taken. This document describes the analyses conducted to develop the Tampa Bay Water Drought Mitigation Plan. 1. Background and Introduction The Tampa Bay region has experienced numerous occurrences of reduced rainfall and water shortages over the years. In the past, utilities and regulatory agencies have responded to such conditions when they occur, rather than having a policy in place to proactively manage these acute water shortages. Because of the difficulties encountered in predicting drought conditions, it is advisable to have a drought mitigation plan which defines management policies, strategies, and actions ready for implementation when drought occurs. In May 2000, the National Drought Policy Commission determined that the focus regarding drought responses must shift from relief to readiness by proactive participation of all involved entities to reduce vulnerability to drought by initiating drought planning, plan implementation, and proactive mitigation of drought impacts. The National Drought Mitigation Center provides four operational drought definitions: 1. Meteorological drought: Departure from normal rainfall over some period of time 2. Agricultural drought: Insufficient soil moisture to meet crop needs 3. Hydrological drought: Deficiencies in surface and groundwater supplies 4. Socioeconomic drought: When physical water shortages affect people, individually and collectively For drought planning to be proactive, quantitative hydrologic indices must be developed to reflect the severity of the drought and trigger pre-determined mitigation actions. Additionally, triggers must indicate not only rainfall shortages, but must also be linked to local water supplies so that they can be managed effectively to meet demand during rainfall-driven water shortages. The National Drought Policy Commission further states that drought mitigation plans should be comprehensive in the mitigation options that are specified. Such comprehensive mitigation plans include demand reduction, operations, and supply augmentation as part of a drought response. The Southwest Florida Water Management District (SWFWMD) Water Shortage Plan developed under Subsection (1), Florida Statutes, defines specific actions to be taken at various phases of declared water shortage emergencies. These phases have been defined as moderate, severe, and extreme water shortage conditions. The process of declaring a water shortage, however, is relatively subjective, and lacks any predetermined triggers to automatically initiate any of the three drought phases. Further, the SWFWMD plan lacks TPA/W:/W155797/DMP FINAL REPORT1_ DOC 1

7 specific quantifiable reduction goals for the three named phases. Lastly, the plan does not include augmentation of supply as a component of drought management, and limits the ability to effectively inform and motivate public action. 2. Project Objectives At the November 18, 2000, Tampa Bay Water Board of Directors meeting, the Board directed staff to initiate a drought mitigation planning process in coordination with the SWFWMD and Tampa Bay Water s member governments. The Board also directed staff to work with the SWFWMD to develop a drought mitigation rule that includes specific targets and actions for implementation during future droughts. To fulfill the Board directive, the objectives of this project are twofold: 1. To identify quantifiable drought indices that define levels of drought and related water supply shortfalls, which trigger mitigation actions (e.g., triggers) 2. To pre-determine the demand reduction and supply augmentation actions that will be implemented at specified levels of drought With triggers and specified actions in place, the resulting DMP is intended to provide a water supply strategy that can be implemented during times of such hydrologic drought that limit Tampa Bay Water s water supplies. This plan will differ from historical water shortage approaches used by the SWFWMD by including hydrologic triggers associated with specific demand management and supply augmentation actions, and not just demand management measures. 3. Drought Management Plan Technical Advisory Committee (DMP TAC) The initial step in achieving this Board directive was creation of a Drought Mitigation Planning Technical Advisory Committee (DMP TAC) comprised of representatives of Tampa Bay Water s member governments and the SWFWMD. The first of a series of regular monthly meetings was held January 4, Twenty-one attendees were present, representing all member governments and the SWFWMD. The following personnel represented their respective member governments, agencies, or SWFWMD. Bill Johnson, City of St. Petersburg Public Utilities Patti Anderson, City of St. Petersburg Public Utilities Joan Bradshaw, City of St. Petersburg Public Utilities Rich McLean, Pinellas County Public Utilities Pick Talley, Pinellas County Public Utilities Mike McWeeny, Hillsborough County Water Department Pamela Marlowe-Green, Hillsborough County Water Department Jim Jeffers, Hillsborough County Water Department Norm Davis, Hillsborough County Water Department TPA/W:/W155797/DMP FINAL REPORT1_ DOC 2

8 Dave Tippin, City of Tampa Water Department Mike Bennett, City of Tampa Water Department Glenn Greer, Pasco County utilities Annemarie Gueli, Pasco County Utilities John McKeon, City of New Port Richey Dave Moore, SWFWMD Bobby Lue, SWFWMD B.J. Jarvis, SWFWMD Jay Yingling, SWFWMD Sydney Park Brown, Hillsborough County Coop. Extension Service Alison Adams, Tampa Bay Water Dave Bracciano, Tampa Bay Water Warren Hogg, Tampa Bay Water Nisai Wanakule, Tampa Bay Water Jeff Geurink, Tampa Bay Water Topics discussed at the inaugural DMP TAC meeting included: Drought condition indicators such as rainfall deficit, reduced river flows, decreased groundwater elevations, and long-term forecasts Drought management planning approaches, including a comprehensive early warning system, a risk and impact assessment procedure, mitigation and response strategies, and community awareness and education Possible elements of a DMP for Tampa Bay Water, including quantifiable triggers for action, specific short-term and long-term actions in response to triggers, assessment of the implemented actions, coordination with SWFWMD and member governments, and communication and education strategies 4. Project Approach Participants at the January 4 th meeting agreed that development of a DMP containing hydrologic triggers was necessary. The approach for this project divided the activities into two phases. Phase I of this project involved the following: Preliminary assessment of rainfall, surface water, and groundwater data for development of triggers Conceptual integration of the rainfall, surface water, and groundwater triggers Identification of possible demand reduction, operational, and supply augmentation actions Conceptual DMP decision process and plan Development and approval of a technical scope of work and schedule to complete the DMP TPA/W:/W155797/DMP FINAL REPORT1_ DOC 3

9 Phase II activities involved the following: Final development of the triggers Final drought mitigation plan Communications plan Rule-making strategy that would be applied in working with the SWFWMD during the Water Shortage rule-making process 5. Phase I Drought Mitigation Plan Development Phase I focused on development of a conceptual drought mitigation process through a series of meetings/workshops with the DMP TAC. The objective of these meetings was to identify drought management approaches and to build consensus among members that a regionwide, long-term drought management process was needed. This included developing strategies to deal with the ongoing ( ) drought. At the onset of the project, it was hypothesized that surface water and groundwater levels could be related to rainfall, and that such a relationship could be used to establish action triggers at various levels in the plan. Intuitively, surface water would seem to respond quickly to an increase or decrease in rainfall. However, variations in groundwater elevations would be expected to lag in response to corresponding increases or decreases in rainfall. This hypothesis was tested by analyzing sample data for the Tampa Bay region. The goal of this analysis was to examine the data set for possible relationships between rainfall, surface water flow, and groundwater elevations, and develop triggers to initiate drought mitigation actions. Each variable was examined individually and then compared to each other to establish possible trends. 5.1 Phase I Triggers Drought mitigation action levels (triggers) were determined by visual examination for the period of analysis data ( ) used in the preliminary analysis. This period of record was selected for use in the Phase I analyses because this provided a sufficient period to analyze the then-current (2000) drought situation and complete a preliminary assessment of rainfall, surface water and groundwater relationships. Historical (period of record) daily rainfall data was obtained from selected rainfall stations within Tampa Bay Water s service area. Daily average rainfall for the region was determined as an average of rainfall recorded at individual stations. The regional average monthly rainfall was then calculated as a sum of average daily rainfalls for a given month. A rainfall-deficit approach was developed in the Phase I analysis because surface water flows and groundwater levels respond to deviations from normal rainfall. The deficit was defined as the difference between the historical monthly average rainfall and the actual monthly rainfall for a given month. Also to simplify the drought trigger mechanism, developing a single index (i.e., regional rainfall deficit) was desirable. Rainfall deficits were calculated from historical monthly average rainfall and the actual monthly rainfall data. Cumulative rolling rainfall deficits for 3-month, 6-month, 9-month, and 12-month periods TPA/W:/W155797/DMP FINAL REPORT1_ DOC 4

10 were then calculated and evaluated as potential trigger mechanisms. These deficits would be used later to compare changes in surface water and groundwater levels with rainfall. The 12-month rolling cumulative rainfall deficit scenario was selected to develop the rainfallbased decision process for the Phase I analysis. This decision was based on the strong influence of seasonal variations on the shorter-term rolling deficits (3-month or 6-month). The 12-month rolling cumulative rainfall deficit reduces the influence of normal dry season rainfall variability and provides a better index for long-term rainfall shortages which affect surface water supplies. Flow in the Hillsborough River was analyzed for the surface water example in the Phase I analysis. Flow deficits were calculated in a manner similar to the rainfall example, based on the difference between historical monthly flow averages and actual monthly flow for a given month. The period of record for this analysis was October 1995 to December These flow deficits were then compared to the 12-month rolling cumulative rainfall deficits calculated above. A plot of the actual monthly flow to the historical average monthly flow, 12-month rolling cumulative flow deficit, and the 12-month rolling cumulative rainfall deficit was made and evaluated. Inspection of the graphical results showed that Hillsborough River flow responds rapidly to changes in rainfall. This is expected due to the sensitivity of river flow to increases or decreases in rainfall. Groundwater elevation data from Floridan aquifer monitoring wells (Lutz Lake Fern, Pasco Well 13, SR-577) and surficial aquifer wells (Lutz Lake Fern - shallow, SR-577) were analyzed and compared to the 12-month rolling cumulative rainfall deficits. Surficial aquifer wells were determined not to be good triggers for drought mitigation for several reasons: The surficial wells are not a part of the regional supply source Their hydrology is not regional in nature Their elevation data is volatile and flashy, reacting to changes in the local environment Groundwater elevation data from the deep wells was analyzed and deficits were calculated in a manner similar to the rainfall and surface water deficits. These deficits were then compared to the 12-month rolling cumulative rainfall deficits calculated above. A comparison of the historical groundwater elevation, actual groundwater elevation, 12- month rolling elevation deficit, and the 12-month rolling rainfall deficit for the SR-577 deep well was evaluated for the period of analysis ( ). As expected, a considerable lag was evident in groundwater elevation changes as a function of rainfall. For example, a continuous decrease in rainfall deficit (i.e., increased rainfall) was observed from March 1997 to March Yet groundwater elevations did not start to rise until November In fact, groundwater deficits continued to increase from March 1997 to November 1997, even though the rainfall deficit continued to decrease over the same period. Similarly, an increase in rainfall deficit from March 1998 to November 2000 was followed by a corresponding increase in groundwater elevation deficits, with a considerable lag. The Phase I technical memorandum (June 2001) describes the results of the Phase I analysis. The results of the Phase I study suggested consistent relationships between rainfall, surface water flows, and groundwater elevations. However, the change in groundwater elevations lagged considerably after the increase or decrease in rainfall. A comparison of 12-month TPA/W:/W155797/DMP FINAL REPORT1_ DOC 5

11 rolling deficits for all three parameters indicated that surface water flows responded rapidly to an increase or decrease in rainfall. Over an extended period of time, however, groundwater elevations do indeed follow the rainfall deficit trend. 5.2 Conceptual Phase I Drought Mitigation Process and Plan A conceptual drought mitigation process was developed based upon 12-month rolling deficits for rainfall, surface water flow, and groundwater elevations. Based on the preliminary analysis, a combination of triggers could be used to indicate severity of drought and impacts to water supply. For example a moderate (or Level 1) drought would trigger certain actions. As the rainfall deficit continued and impacts to surface supplies became evident, additional actions would be taken. In the most severe cases, groundwater would be impacted and would trigger yet another set of actions. Figure 1 illustrates the relationship between levels of drought, types of triggers, and possible actions. Considering the relationship between the various triggers, a conceptual DMP was developed, which included demand reduction, operational, and supply augmentation actions. The following assumptions were applied in developing the conceptual DMP: A normal state (non-drought condition) of two-day per week watering restrictions will remain in place indefinitely Demand management actions and enforcement or restrictions will be applied uniformly across the region Distribution system operations will vary by member government Public awareness will be uniform and will occur throughout the process Demand management actions for Level I could include drought announcements and increased enforcement of the two day per week watering schedule. Level II actions could include continuing public awareness and education, one day per week watering restrictions, a designated percent reduction in demand, and implementation of a drought surcharge on water rates. Level III actions could include further public awareness and education, zero days per week watering restrictions (although not selected as an option), and further percent reduction in demand. Operational changes include activating additional constraints inside the Optimized Regional Operations Plan (OROP) to shift production to the least-impacted sources at each level of drought. For example, groundwater production might need to be increased in response to reduced surface water availability. Additionally, supply augmentation for Level II could include augmentation from preselected sources (i.e., Morris Bridge Sink and Tampa Bay Desalination project [Desal I]) and activation of member/system interconnects. Level III actions could include temporary exceedance of groundwater permits as controlled by the OROP to meet demand. Table 1 summarizes the conceptual DMP developed during Phase I. TPA/W:/W155797/DMP FINAL REPORT1_ DOC 6

12 Action Levels Link Triggers and Decision Process Drought Level I Level II Level III Trigger Rainfall Rainfall Surface Water Rainfall Surface Water Groundwater Action Demand Reduction Operation Supply Augmentation FIGURE 1 Phase I Relationship Between Level of Drought and Possible Mitigation Actions Tampa Bay Water DMP TPA/W:/W155797/DMP FINAL REPORT1_ DOC 7

13 TABLE 1 Conceptual Drought Mitigation Plan Level Demand Management Operations Supply Augmentation Level I Drought announcement Uniform, increased enforcement of 2 day per week lawn watering restrictions Activate OROP Level I drought constraints Level II 1 day per week lawn watering restrictions, with uniform enforcement X % reduction in regional and member monthly per capita demand Member government operational efficiency Activate OROP Level II drought constraints Begin augmentation from pre-selected sources Activate member/system interconnects Implement drought surcharge on water rates Level III Zero days per week lawn watering restrictions X+ % reduction in regional and member monthly per capita demand Activate OROP Level III drought constraints Planned temporary exceedance of groundwater permits Planned temporary exceedance of secondary drinking water standards 5.3 Phase I Conclusions The DMP TAC recommended, at the end of the Phase I analysis, the triggers that were developed must be linked to Tampa Bay Water s supply capacity. Triggers must be set that actually impact the ability to supply water at any given point in time. For example, drought mitigation triggers over the short term would be developed based on Tampa Bay Water s existing supply capacity. As new sources and capacity were developed and brought online, however, these triggers would be revised to account for the increased capacity. Therefore, any DMP developed for Tampa Bay Water must allow for modification of these triggers on a continual basis. The conclusions supported by the DMP TAC are summarized as follows: DMP participants agreed that the drought mitigation process was needed and beneficial The final DMP should include regional hydrologic triggers The DMP would aid in communication and credibility with the public though consistent and defined triggers and actions Preliminary analysis of rainfall, surface water, and groundwater data showed consistent trends in relation to drought TPA/W:/W155797/DMP FINAL REPORT1_ DOC 8

14 Preliminary analysis showed that rainfall, surface water, and groundwater triggers could be associated with levels of drought The Phase II analysis must address potential impacts to supply Tampa Bay Water member governments did not support the demand management action of zero watering days 6. Phase II Drought Mitigation Plan Development 6.1 Data Analysis The Phase II analysis extended the period of record used to evaluate historical rainfall, surface water flows, and groundwater level data, and expanded the number of rainfall and surface water flow sites evaluated. Rainfall data from regional rainfall stations, historical surface water flows from the Hillsborough and Alafia rivers, and historical groundwater levels from regional Floridan aquifer monitoring wells were used to conduct the Phase II analyses. The deficit analysis described in Section 5.1 was used to relate rainfall, surface water, and groundwater responses. A 12-month rolling cumulative rainfall (RCRF) deficit was selected because it reduces the influence of normal dry season rainfall variability and provides a better index for long-term rainfall shortages which affect surface water supplies. The data used and results of the analysis are summarized below. Figures A1 through A6 are included as Appendix A. Rainfall Analysis Six regional rainfall stations using complete period of record data through September 30, 2001: St. Leo (SWFWMD) Tampa International Airport (SWFWMD) Tarpon Springs (SWFWMD) Plant City (SWFWMD) Cypress Creek Plant (Tampa Bay Water) South-central Hillsborough (Tampa Bay Water) Rainfall Analysis Results Regional deficit generally representative of individual stations Recent trends ( ) consistent with historical record Drought and rainfall surplus events are recurring in the historical record and can be expected to reoccur in the future Exceptional surplus events include 1960 and 1998 Surface Water Analysis Hillsborough River flow at the Morris Bridge gage period of record ( ) Alafia River flow at the Lithia gage period of record ( ) TPA/W:/W155797/DMP FINAL REPORT1_ DOC 9

15 Surface Water Analysis Results Historical pattern fluctuates between surplus and deficit Exceptional surplus events correspond with exceptional rainfall events Flow deficits strongly correlate with rainfall deficits as shown in Figures A1 and A2 for the Hillsborough River and Alafia River, respectively. Flow deficits are affected by rainfall-deficit duration as well as magnitude of the rainfall deficit Groundwater Analysis Based on eight SWFWMD central region index wells with varying periods of records (Figure A3) Groundwater Analysis Results Water level data highly variable since 1981 Water level trends not consistent between wells Regional deficit highly affected by several wells Definite trend with time, water-level deficit and recovery apparent but lags rainfall Not conducive for DMP triggers because of response lags and lack of correlation with rainfall deficit Figure A3 depicts the changing and variable nature of groundwater levels in the index wells. 6.2 Conclusion Rainfall-deficit based triggers were established by a detailed analysis of historical rainfall and corresponding river flows in the tri-county region. The analysis showed a significant reduction in surface water flows of the Hillsborough River and Alafia River when the regional 12-month RCRF deficit exceeded 10 inches (Figures A1 and A2). The analysis also showed that the duration of rainfall deficit and the magnitude of rainfall deficit are important factors in evaluating surface water flow responses. 6.3 Impacts on Supply The next step of the Phase II analysis evaluated the relationship between hydrologic drought triggers and available supply. For planning purposes, the plan was designed for implementation after January 2003 when System Configuration 1 supplies are online, with and without the regional reservoir operational. At that time, the following conditions and/or supplies will be in place: 1. Wellfield pumpage from the Consolidated Wellfields will be reduced to 121 mgd, 12-month running annual average 2. The regional surface water treatment plant will be online and capable of treating 66 mgd 3. Brandon Urban Dispersed Wells (BUDW) will be operating at 6 mgd annual average TPA/W:/W155797/DMP FINAL REPORT1_ DOC 10

16 4. Desalination I will be online, base-loading the system with 25 mgd 5. The analysis was conducted with and without the regional reservoir operational In addition to these conditions, other sources that are traditionally available were considered in the analysis, including the South-Central Hillsborough (SCH) Wellfield and the City of Tampa supplies. Figure 2 shows all of the supplies that will be available in 2003 and which were specifically included in this analysis. Desal. I 25 MGD Emergency Supplies Morris Bridge Sink Other TBD SWTP 66 MGD Consolidated Wellfields 121 MGD (2003) Brandon Urban Dispersed Wells (BUDW) 6 MGD TBW System Tampa SWTP Tampa DEMAND Tampa Hillsborough River Reservoir ASR Hills/TBC Alafia Regional Reservoi r SCH Wellfield 24.1 MGD TBW DEMAND -Normal -Drought Surface Water Ground Water Other Specific Source FIGURE 2 Tampa Bay Water Supply Capacities Beginning January 2003 Tampa Bay Water DMP The available capacity from the system shown in Figure 2 was modeled using permitted Enhanced Surface Water System (ESWS) withdrawals, a reservoir stage model (HDR, 2000), City of Tampa Water supply system (including aquifer storage recovery [ASR]), Desal I, BUDW, and the SCH Regional Wellfield. For this analysis the hydrologic data period of record used was 1977 through September This period of record was selected for the supply/demand analysis because historical flow data in the Alafia River prior to 1977 are unreliable for a supply analysis and flow from Lithia Springs (which is needed for the supply analysis) is not available prior to TPA/W:/W155797/DMP FINAL REPORT1_ DOC 11

17 For this analysis, a typical regional annual demand of 244 mgd was used (Water Year 2001 demand was 237 mgd). This annual demand was varied monthly. A repeating pattern of the monthly regional demands were then used to determine the production required from the Consolidated Permit wellfields to provide supply that equaled demand. This analysis did not include an increase in water demand due to growth or a reduction in demand due to conservation. Both factors may cause the actual demand to differ from the amount used in this analysis. The analysis was performed with and without the regional reservoir since it will not be fully operational when production from the Consolidated Permit wellfields is reduced in This allowed determination of drought conditions which would possibly cause production from the Consolidated Permit wellfields to exceed their regulatory limits. DMP triggers were selected based on the hydrologic conditions leading to the supply deficits. Rainfall-based deficit triggers were established as described previously, using the 12-month RCRF deficit. The analysis showed a significant reduction in surface water flows in the Hillsborough River and Alafia River when the regional 12-month RCRF deficit exceeded 10 inches. The decline in available surface water flows forecasts a potential reduction in ESWS supply. The results of these analyses without the regional reservoir and with the regional reservoir are shown Figures A4 and A5, respectively. Figures A4 and A5 are included in Appendix A. 6.4 Development of Recommended Triggers The rainfall deficit analysis was combined with the supply/demand analysis described above to select appropriate RCRF deficit trigger levels that could lead to supply shortages (Table 2). The 12-month RCRF deficit level of 10 inches was selected as the initial DMP trigger and defined as a Level I drought alert, since this rainfall deficit corresponds to a decline in surface water flows and forecasts a potential reduction in supplies from the ESWS if hydrological conditions persist. The alert level allows sufficient time to notify the public of conditions which may lead to a reduction in supplies. As shown in Table 2, two other levels of drought were defined: Level II (water shortage) and Level III (water supply crisis). The Level II water shortage trigger was established at an RCRF deficit-duration, which resulted in significantly reduced ESWS production and rapidly declining reservoir levels. Based upon the hydrologic period of record ( ), this occurred routinely when the RCRF deficit averaged greater than 10 inches over six months. The Level III water supply crisis trigger was established when ESWS production is expected to reduce to near zero production levels and significantly impacted Tampa Bay Water s ability to meet regional demands. Based upon the hydrologic period of record ( ), this appears to occur after 12 or more months of Level II drought conditions. In fact, it has only occurred once since 1977 ( drought) within the Tampa Bay region. The historical RCRF deficits were also compared to ESWS flows and allowable withdrawals to simulate reservoir conditions under varying hydrologic conditions. Reservoir-based triggers were then selected for Level II and Level III conditions corresponding to reservoir stages for 90 days and 30 days of remaining supply at a withdrawal rate of 66 mgd, respectively. Therefore, the DMP levels are initiated using either the rainfall-based or reservoir-based triggers depending upon hydrologic conditions and supply availability. Triggers to move out of the drought and cease actions were also developed. The triggers are TPA/W:/W155797/DMP FINAL REPORT1_ DOC 12

18 designed to correspond to available supplies, and to allow sufficient time for the public to be notified and respond to both entering and exiting drought-induced water supply shortages. TABLE 2 Drought Mitigation Plan: Recommended Triggers Drought Levels On Triggers Off I. Drought Alert RCRF Deficit 10 RCRF Deficit 5 II. Water Shortage III. Water Supply Crisis 6 month average RCRF Deficit 10 or Reservoir Elev. < 102 (90 days of 66 mgd) At Water shortage for 12 months or Reservoir Elev. < 87 (30 days of 66mgd) RCRF Deficit 10 or Reservoir Elev. > 109 (120 days of 66 mgd) 6 month average RCRF Deficit 10 or Reservoir Elev. > 102 (90 days of 66mgd) Note: RCRF = 12-month rolling cumulative rainfall deficit Table 3 summarizes how the rainfall-based triggers would be applied if historical hydrologic conditions ( ) return in the future. The summary shows that a Level I drought alert could occur nine times in 25 years, a Level II water supply crisis could occur five times (once since 1986), and a water supply crisis could occur once ( ). It is important to note that based on 70 years of rainfall data ( ), the Tampa Bay area has experienced only once the level of the drought, both in terms of rainfalldeficit-duration and effects on surface water flows. TABLE 3 Summary of Historical Rainfall-Based Drought Triggers Drought Alert Water Shortage Water Supply Crisis Water Shortage Drought Alert Out of DMP RCRFD 1 >= 10" 6 mo. RCRFD Average >= 10" At Water Shortage for 12 months 6 mo. RCRFD Ave. < 10" RCRFD < 10" RCRFD < 5" 5/1/1977 8/1/1977 9/1/ /1/ /1/1977 3/1/1978 4/1/1981 7/1/1981 8/1/1981 1/1/1982 2/1/1985 5/1/1985 8/1/ /1/ /1/1989 8/1/ /1/1990 5/1/1991 5/1/ /1/1992 3/1/1994 7/1/1994 3/1/1997 9/1/1997 9/1/1999 1/1/ /1/2000 7/1/2001 Number of Occurrences RCRFD - 12-month Rolling Cumulative Rainfall Deficit TPA/W:/W155797/DMP FINAL REPORT1_ DOC 13

19 7. Supply Augmentation Options The demand and supply analysis described in the previous section indicated water shortages under extreme drought conditions. To meet regional demands during these periods, Tampa Bay Water must identify supply augmentation options. Morris Bridge Sink has been identified and approved as one such option. The Morris Bridge Sink was used as an emergency supply source during the drought. The Sink was used from May 30, 2000 to August 14, 2000 and from December 6, 2000 through July 17, 2001, during those two periods pumpage averaged 6.7 mgd and 8.3 mgd, respectively. In addition, increasing desalination production from 25 to 35 mgd was also identified as an emergency source of supply. This additional 10 mgd is not permitted. Due to the lack of operational experience with the Tampa Bay Desalination water supply, increasing this source by 10 mgd was removed from consideration as an emergency source for the DMP. Other than these two possible additional sources, no alternative sources were identified for Tampa Bay Water to use in an emergency drought situation. Morris Bridge Sink is specified as a supply augmentation source in the DMP, and its use will be triggered in a Level II water supply shortage. Existing groundwater supplies represent the only remaining source. The DMP recommends temporary exceedance of the Consolidated Permit regulatory limits to meet demand during a Level III water supply crisis. When the ESWS production is extremely low, Morris Bridge Sink is operating, and less than 30 days of supply (at a rate of 66 mgd) remains in the reservoir, the ability to exceed the Consolidated Permit regulatory limits would allow Tampa Bay Water to meet member demands. Based on the hydrologic period of record ( ), this temporary exceedance may have been required only once in the last 25 years; during the drought. No other sources are available to meet emergency conditions. The ability to rely on temporary use of groundwater resources and infrastructure avoids the need to construct costly new supplies, which would only be needed during these very infrequent conditions. In conjunction with long-term reductions in groundwater withdrawals, the hydrology of the areas affected by the Consolidated Wellfields is expected to rebound significantly, if with temporary periods of high groundwater use. An analysis was conducted to illustrate how the use of the Morris Bridge Sink during Level II water shortage situations may reduce the potential for exceeding the regulatory limit at the Consolidated Wellfields. The rainfall deficit-based triggers (see Table 3) were used to activate the Sink; it was assumed that 15 mgd from the Sink would be available to meet demand. Results of this analysis are shown on Figure A6. Based on this analysis, the Morris Bridge Sink could have been used for up to 18 months during the drought. The use of the Sink at a rate of 15 mgd would avoid exceedance of the Consolidated Wellfield regulatory limit of 121 mgd; given similar regional water demands as used in the analysis. In addition, the use of Morris Bridge Sink would allow Tampa Bay Water to continue operating the regional surface water treatment plant and reduce potential source water quality problems as the reservoir stage is reduced. Morris Bridge Sink was actually used for approximately nine months during the drought. There are several reasons for the difference between the actual use and its potential for use during future droughts. Reasons include regulatory constraints, infrastructure TPA/W:/W155797/DMP FINAL REPORT1_ DOC 14

20 constraints, and the significant use of the Tampa Bypass Canal by Tampa Bay Water to augment the City of Tampa s reservoir. It is assumed that Tampa Bay Water will pump all available surface water from the Tampa Bypass Canal to the regional surface water treatment plant after January Regulatory and infrastructure constraints are currently being addressed by Tampa Bay Water. 8. Demand Management Actions The conceptual DMP developed in Phase I included a wide range of demand reduction measures. During Phase II, these options were presented to and discussed with each member government. The options considered included: Uniform enforcement of two day per week watering restrictions Prescribed percentage reductions Drought surcharges No watering days per week Operational measures to be implemented by members While each of these alternatives has been effective in reducing demands in the Tampa Bay area and other regions of the United States, some were not acceptable to Tampa Bay Water members for a number of reasons. Therefore, the proposed DMP includes only irrigation restrictions for Levels I and II. If a water supply crisis occurs, however, Tampa Bay Water and its member governments will need to implement quantifiable water-saving measures. These might include zero watering days per week, prohibition of all non-essential uses of water, drought surcharges, and other measures. During a water supply crisis, actual reductions in demand will correspond to an extension in the remaining reservoir supplies. 9. Communications Strategy Consistent communication of drought messages to the public is fundamental to the success of the DMP. To develop this drought mitigation communications plan, communications plans and specific outputs (advertisements, media coverage, etc.) were collected from Tampa Bay Water, the member governments, and the SWFWMD. Additionally, a meeting was held with representatives of the member governments to further discuss elements of their plans. The information on key messages and methods of communication provided invaluable insight into elements of the drought mitigation communications plan. Tampa Bay Water, SWFWMD, and Member Government Communications Plans Several key messages were common to all of materials collected from Tampa Bay Water, the SWFWMD, and member governments. These common messages regarding the drought were: The Tampa Bay area is in a severe drought Increased rainfall is helping, but the drought is not over yet The public is a key player in conserving water Details on current water restrictions and penalties for violation TPA/W:/W155797/DMP FINAL REPORT1_ DOC 15

21 The drought message has been communicated to water customers by Tampa Bay Water, SWFWMD, and the member governments through a wide variety of media outreach activities and direct public communications methods. These methods, which have successfully conveyed key messages, include the following: Media Outreach Press releases Press conferences Newspaper articles Newspaper ads TV/Radio Public Service Announcements Local Cable TV programs Public Communication Brochures Web sites Bill inserts Messages printed on bills Direct mail Newsletters Communications Plan for Drought Mitigation The drought mitigation communications plan begins with a media strategy for the Drought Mitigation Planning effort to be used by Tampa Bay Water, the SWFWMD, and the member governments. This media strategy consists of key messages that point out triggers and current drought conditions, actions being taken, and what the public can expect next. Tactics for communication are also included. These tactics were selected based on insights gained from the review of communications plans gathered from the member governments. The goal of the media strategy is that all parties convey the key messages at the onset of a drought level declaration. The communications plan includes an element for individual member governments to communicate information specific for them, along with key messages prepared from the media strategy. The communications outline for all drought levels is structured as follows: Media Strategy Tampa Bay Water, SWFWMD and member governments Uniform outreach to media (e.g., meteorologist) Key Messages Triggers/current conditions Actions taken What s next Tactics Communications TBD by member governments Key messages from media strategy Information specific to member governments Supplies Additional restrictions Conservation TPA/W:/W155797/DMP FINAL REPORT1_ DOC 16

22 Specific Drought Media Strategies Table 4 outlines examples of key messages and methods to transmit them to the public. Each level of drought outlined in the DMP has a specific set of messages, along with methods to convey those messages to the public. Tampa Bay Water, the SWFWMD and the member governments should use these messages concurrently when a drought level is declared. TABLE 4 Key Drought Messages and Delivery Methods Key Messages Level I Level II Level III Drought Alert Water Shortage Water Supply Crisis Triggers/current conditions 10 rainfall shortage means we are in a Level I drought 10 rainfall shortage has lasted for six months and means we are in a Level II water shortage; reservoir levels indicate approximately 90 days of supply 10 rainfall shortage has lasted for 12 months and means we are in a Level III water supply crisis; reservoir levels indicate approximately 30 days Actions Taken 2 day/week watering restrictions are in effect 1 day/week watering restrictions are mandatory Implement options for measurable demand reductions What s next If rainfall shortage lasts for six months, a Level II water shortage will be declared If rainfall shortage lasts for 12 months, a Level III water supply crisis will be declared Restrictions will be eased when rainfall deficit decreases Tactics Press release Local cable TV Newsletters Brochures Press conference TV/Radio promo Spokesperson interviews Press conference TV/Radio specials Spokesperson interviews Newspaper articles Letters to editor Newspaper Ads 10. Drought Mitigation Process and Plan Based on the analyses described in this document, the recommended DMP includes rainfallbased and reservoir-based triggers, demand management actions, and supply augmentation. A proactive plan such as this will provide Tampa Bay Water with an operational tool to meet its water supply obligations in times of water supply shortages resulting from hydrologic drought conditions. Figure 3 depicts the recommended drought mitigation decision process. Table 5 summarizes the proposed DMP triggers with corresponding demand reduction and supply augmentation actions. TPA/W:/W155797/DMP FINAL REPORT1_ DOC 17

23 Drought Mitigation Decision Process Routine Rainfall Monitoring: Calculate 12 Month Rolling Cumulative Rainfall (RCRF) Deficit Exit DMP Yes Is RCRF Deficit < 5 inches? No Is RCRF Deficit > 10 inches? No Yes Level I Drought Alert Initiate drought related public messaging Is 6 Month avg of the RCRF Deficit > 10? Yes Level II Water Shortage Actions No Has Level II persisted for 12 consecutive months? No Yes Level III Water Supply Crisis Actions FIGURE 3 Drought Mitigation Decision Process Tampa Bay Water DMP TPA/W:/W155797/DMP FINAL REPORT1_ DOC 18

24 TABLE 5 Drought Mitigation Plan: Triggers and Actions Drought Levels On Triggers Off Demand Management Actions Supply Augmentation I. Drought Alert RCRF Deficit 10 RCRF Deficit 5 Initiate public messaging and Increase effectiveness of 2 day per week lawn watering restrictions (e.g., enforcement) II. Water Shortage 6 month average RCRF Deficit 10 or RCRF Deficit 10 or 1 day per week lawn watering restrictions Morris Bridge Sink On: Approximately 15 mgd Reservoir Elev. < 102 (90 days of supply) Reservoir Elev. > 109 (120 days of supply) III. Water Supply Crisis At Water shortage for 12 months or Reservoir Elev. < 87 (30 days of supply) 6 month average RCRF Deficit 10 or Reservoir Elev. > 102 (90 days of supply) Members implement options for measurable demand reduction Optimize all supplies to meet demand, including temporary exceedance of Consolidated Wellfields Permit Note: RCRF = 12 month rolling cumulative rainfall deficit Days of remaining reservoir supply are approximate and based on a withdrawal rate of 66 mgd. Conclusion With triggers and specified actions in place, the resulting DMP provides a water supply strategy that can be implemented during times of such hydrologic drought that limit Tampa Bay Water s water supplies. As new water supply sources are brought online and operational experience with the ESWS increases, the DMP will be revised. The plan is designed to allow triggers and actions to be modified as needed. This plan differs from historical water shortage approaches used by the SWFWMD because it includes hydrologic triggers associated with specific demand management and supply augmentation actions, and not just demand management measures. This approach will aid in communication and credibility with the public through consistent and defined triggers and actions. TPA/W:/W155797/DMP FINAL REPORT1_ DOC 19

25 Appendix A Appendix A

26 Appendix A Figure A1: Hillsborough River Flow Deficit Analysis Figure A2: Alafia River Flow Deficit Analysis Figure A3: Groundwater Level Deficit Analysis Figure A4: Demand vs. Supply Without Regional Reservoir Figure A5: Demand vs. Supply With Regional Reservoir Figure A6: Demand vs. Supply Without Regional Reservoir with Morris Bridge Sink