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HomeMy WebLinkAboutMulti-Hazard Mitigation Plan: 14. Droughts CIVIL DEFENSE AGENCY COUNTY OF HAWAII 920 ULULANI STREET HILO,HAWAII 96720 r f • 14. Droughts Chapter 14:Hazard Analysis—Droughts CHAPTER 14 - DROUGHTS 14.1 Description of Hazard 14.1.1 Defining and Measuring Drought Drought can be defined in relative or absolute terms. Relative drought is determined by the fluctuations about average local conditions. Absolute drought refers to a single uniform level. Relative drought recognizes that the severity of drought impact varies according to the adaptations and vulnerability of natural and social systems relative to prevailing normal conditions. Absolute drought is used primarily by researchers interested in large drought- impacted areas. Relative drought is useful to examine drought conditions on this island. Much of the information presented in this section was drawn from portions of a statewide drought study(the"Hawaii Drought Plan") applicable to the Island of Hawai'i.67 Drought differs from other natural hazards in three significant ways. First, a drought's onset and end are difficult to determine since the effects accumulate slowly and may linger even after the apparent termination of an episode. Second,the absence of a precise and universally accepted definition adds to the confusion about whether a drought exists, and if it does, the degree of severity. Third,unlike most other natural hazards, drought impacts are less obvious and are spread over a larger geographic area. These characteristics have hindered the development of accurate,reliable, and timely estimates of drought severity and effects. Of the several indicators used to measure drought, the most common is rainfall. A dense network of rain gauges, and long term collected, collated, and published data provide an excellent record of historic rainfall patterns and spatial variations on each Hawaiian Island. There are two popular drought indices. The Palmer Drought Severity Index (PDSI) was not appropriate for Hawaii and it was decided that the Standardized Precipitation Index (SPI) should be used as an initial drought index for the state. The Standardized Precipitation Index (SPT) was developed by Thomas McKee at Colorado State for use as a drought monitoring tool and has been embraced by agencies such as the National Drought Mitigation Center and the Western Regional Climatic Center. The beauty of this index is its simplicity because it uses only monthly rainfall as its input. This simplicity also makes it ideal for use in Hawaii, where there is a relatively dense network of rain gages. In comparison, the Palmer Drought Severity Index(PSDI),which is in widespread use across the Mainland U.S., is much more complex and requires temperature and soil moisture as additional data inputs. These types of additional data are either sparse or non-existent in Hawaii. Furthermore, the PDSI is more applicable to broad climatic areas and is not suited for representing conditions in the small-scale climatic zones of the Hawaiian Islands. 67 Wilson Okamoto Corp."Hawaii Drought Plan".Prepared for the State of Hawaii,Department of Land and Natural Resources,February 2005 14-1 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts Because the SPI values are normalized, the wide range of rainfall conditions across Hawaii can be assessed on an equal basis. Furthermore, SPI values can be generated for multiple time scales. This is extremely useful for monitoring purposes because drought affects the various sectors over a wide range of time scales. Finally, since the SPI uses standard statistical principles, it can also be used to monitor other data such as stream flow, reservoir levels, and ground water levels. Table 14-1 is an example of a drought classification scheme based on SPI. Table 14-1. Drought Classification Based On SPI SPI Values Designation Time in Category 0.00 to-0.99 Mild Drought 34.1% -1.00 to-1.49 Moderate Drought 9.2% -1.50 to-1.99 Severe Drought 4.4% -2.00 or less Extreme Drought 2.3% The Honolulu Forecast Office (HFO) of the National Weather Service (NWS) has tailored the SPI software for use in Hawaii. At present, 59 sites have been selected as part of the SPI monitoring network. These sites are separated into two groups called the "quick-look sites" and the "standard sites". The "quick-look sites" use data from selected real-time reporting stations that comprise HFO's flash flood monitoring network. Only 16 out of 69 real-time reporting stations are available for use in SPI calculations due to the fact that most of these locations have short periods of record that can result in risky statistical inferences. The main benefit of the "quick-look site" is that the data are available immediately after the end of a month so that SPI values can quickly be determined. The "standard sites" are selected locations from the NWS Cooperative Observer network. Rainfall readings at these sites are taken manually and submitted via mail after the end of the month to the NWS Pacific Region Headquarters for preliminary quality control. The monthly data for the "standard sites" are intercepted at this point and forwarded to HFO for SPI calculations. The SPI method is designed to be flexible in terms of drought duration specified by users. Short-term drought duration (e.g., 3 months) may be important for agricultural practices while long-term duration (e.g., one year or longer) may be vital for water supply management interests. Here, 3-month and 12-month are considered. If 3-month events are desired, a moving average time series is constructed by summing the first three monthly totals. Next precipitations for months 2, 3, and 4 are summed and then precipitations for months 3, 4, and 5 are summed and so on. The resulting time series is then used to compute the 3-month SPI. The 12-month SPI can be obtained in the same manner. The flexibility of multiple SPI time values makes this index attractive because drought affects various sectors across a wide range of time scales. 14.1.2 Causes of Drought Droughts have been postulated to correspond with the global-scale oceanic-atmospheric phenomenon known as ENSO (El Nino-Southern Oscillation). El Nino is the anomalous warming of the eastern equatorial Pacific sea surface. The Southern Oscillation is the seesaw in atmosphere between the eastern and western equatorial Pacific. Various studies have found some correlations but the predictive capabilities for drought events are still in the 14-2 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts developing stages. To complicate matters, global warming climate changes due to increasing atmospheric concentrations of carbon dioxide and other radiation-absorbing gases may change the frequency, intensity, duration, and pattern of droughts. 14.1.3 Impacts of Drought Droughts diminish drinking water supplies, cause agricultural losses, and increase the incidence of wildfires. This island is particularly vulnerable to droughts due to pervasive water catchment systems, reliance on diversified agriculture, and expansive pasture and woodland areas susceptible to wildfires. 14.2 Significant Historic Events Droughts have affected the Hawaiian Islands throughout its history. Farmers, cattle ranchers, and individuals who rely on catchment water systems and surface stream diversions are the communities most immediately affected by drought. Areas susceptible to wildland fires are more vulnerable during very dry conditions, and incidences of wildland fire have increased considerably throughout the State. Droughts have impacted almost every island in Hawaii with the most severe events occurring in the past 15 years associated with the El Nino phenomenon. During the El Nino years, droughts occurred during the winter-spring period. For example, in January 1998, the National Weather Service's network of 73 rain gauges throughout the State did not record a single above-normal rainfall, with 36 gages recording less than 25 percent (%) of the norm (NWS Honolulu Forecast Office). The 0.14 inches of rain recorded for the city of Hilo is the lowest monthly total ever observed for any month since records have been kept. Normal January average rainfall for Hilo is 9.88 inches. Parts of the island of Hawaii continued to receive less than 10% of the normal rainfall until May 1998. Drought conditions will continue to affect Hawaii's environment, but the extent of drought and the respective consequences will probably increase in severity. Severe drought conditions may result in crisis-level shortages in water supplies for human consumption, agricultural irrigation, and fire suppression for severe wildland fire hazards. Crop damage and cattle losses have been major concerns during periods of severe drought, resulting in the implementation of both voluntary and mandatory water- conservation measures. The most recent drought of 1998 to 2003 has wreaked havoc on the farmers and ranchers of Hawaii, especially those on the southeastern end of the State. Ranchers are grass farmers whose cattle suffer from decreased grazing areas during drought conditions. The recent drought left the State of Hawaii with reduced cattle carrying capacity, lower calf production, and lower weaning weights, resulting in an enormous loss of revenue. The consequences of this economic impact are compounded by the additional costs to ranchers for supplemental feed and minerals required to sustain the animals during these periods. The economic impacts of drought on Hawaii's cattle industry (i.e., estimated drought-related loss) for 1999 and 2000 have been evaluated. increased cattle mortality and reduced calving rates led to a direct loss in the total number of marketable cattle. The average live weight for 14-3 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts all marketed cattle in 1999 decreased by about 10% resulting in decreased revenue. In addition to realized financial losses, overall cattle inventory was reduced by lower calving rates and selloff of mature cattle due to the unavailability of inexpensive feed or forage. This inventory reduction will contribute to economic losses for several years following drought resolution. Cattle loss due to death increased by 4% and weaned weights were lower by 89 lbs/head in 1999. The dollar losses are as follows: Drought-Related Impact 1999 Estimated Revenue Loss ($) Reduced wean weight $3,291,241 Reduced calf crop $687,940 Increased mortality $2,495,750 Total: $6,474,931 The total financial loss for the year 2000 in the same areas of cattle-related impacts shown in the above table is estimated at$9,078,360. Most severe droughts on record in Hawaii have occurred during the years associated with El Niflo — 1982/1983 and 1997/1998. According to the Pacific El Niflo-Southern Oscillation Application Center,the dry conditions, in general, have been associated with persistent zones of high-pressure systems throughout the islands. This feature related to El Nino is typical in the tropical Pacific. Table 14-2 summarizes the history of severe droughts. Ongoing Drought Conditions 2008—Present: Drought conditions on Hawaii Island was given its first ever D4 (drought-exceptional) designation in March 2010. West Hawaii rain gages showed that April 2010 rainfall was 50% or less. Similarly, January—April 2010 total rainfall was also 50% or less for the majority of rain gages around the island. October 2009—April 2010 wet-season rainfall was the driest in 30 years of record;ranchers reported the worst drought conditions ever. Hawaii Department of Research and Development reported that in the Kona/Kau districts, the production of coffee and macadamia nuts were down. The floriculture industry had problems with irrigation water supply. In May 2010, DLNR Division of Forestry and Wildlife closed four areas in the Mauna Kea Forest Reserve from the Hilo side of Pohakuloa/Waikahaula to Pun Kemole due to extremely dry conditions. There have been livestock deaths reported in Kawaihae. Parker Ranch is actively managing pastures due to drought by moving herds. In response to the drought conditions, Parker Ranch is culling as needed. Kona coffee farmers are suffering from drought conditions. Coffee trees need steady rainfall beginning from the flowering period in order to produce fruit/berries. For proper growth, coffee tress need 1 inch of rainfall per week. Impacts include the loss of 1/3 of coffee trees and entire harvested coffee crop refused by roaster due to poor berry conditions. Farmers who have access to water are irrigating intensively. Producers that have no county water use rainfall catchments systems. These producers have to pay for water deliveries, which is a financial hardship. Additional drought impacts include feral animals 14-4 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts (pigs) entering producers' fields and orchards destroying crops and damaging irrigation systems. Commission on Water Resource Management issued a press release asking residents and businesses to conserve water and asked people to be aware of increased risk of wildfire due to these drought conditions. Governor Lingle also sent a memo to all State departments asking for water conservation inside and outdoors of State facilities. CWRM's role is to coordinate any drought assistance efforts in the State and to assist counties to prepare and respond to drought. USDA Farm Service Agency reported that on July 14, 2010, the USDA Secretary designated the four counties in Hawaii as disaster areas due to drought. The disaster designation triggers several FSA assistance and loan programs. FSA regular loan program interest rate is lower than the emergency loan interest rate. There are several disaster assistance programs that producers can apply for. These include Supplemental Disaster Assistance Payment Program (SURE), Livestock Forage Disaster Assistance Program (LFP), Livestock Indemnity Program (LIP) Emergency Livestock Assistance Program (ELAP), Tree Assistance Program (TAP), Non-insured Crop Disaster Assistance Program (NAP), Farm Loan Program (FLP), Reimbursement Transportation Cost Program (RTCP), and Emergency Conservation Program (ECP). There is a new FSA program called the Reimbursement Transportation Program, which can reimburse producers' transportation costs for their feed, fertilizer, etc. There is $2.6M available under this program for Hawaii and other U.S. Territories. 14-5 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts Table 14-2. Historic Drought in the Hawaiian Islands Year Areas Remarks 1901 North Hawaii Severe drought,destructive forest fires. 1905 Kona,Hawaii Serious drought and forest fires. 1908 Hawaii and Maui Serious drought. 1912 Kohala,Hawaii Serious drought and severe sugarcane crop damage for ttvo years. 1952 Kauai Long,severe dry spell. 19.53 Hawaii,Kauai,Maui, Water rationing on Maui;water tanks in Kona almost empty;867 head of and Oahu cattle died;pineapple production on Molokai reduced by 30%;rainfall in the 1962 Hawaii and Maui State declared disaster for islands ofHawaii and Maui;crop damage,cattle deaths,and severe fire hazards;losses totaled$200,000. 196.5 Hawaii State water emergency declared;losses totaled$400,000. 1971 Hawaii and Maui Irrigation and domestic water users sharply curtailed. 1975 Kauai and Oahu Worst drought for sugar plantations in 15 years. 1977- Hawaii and Maui State declared disaster for islands ofHawaii and Maui. 1980- Hawaii and Maui State declared disaster;heavy agricultural and cattle losses;damages totaling 1981 at least$ 1.4 million. 1983- Hawaii E1Nitio effect State declared disaster;crop production reduced by 80%in 1985 Waimea/Kamuela area;$96,000 spent for drought reliefprojects. 1996 Hawaii,Maui,and Declared drought emergency;heavy damages to agriculture and cattle Molokai industries;losses totaling at least$49.4 million. 1998 Hawaii and Maui State declared drought emergency for Maui;County declared emergency for Hawaii due to water shortages. 2000- Hawaii,Maui, Counties declare drought emergencies;Governor proclaims statewide drought 2002 Molokai,Oahu,Kauai emergency,Secretary of Agriculture designates all Counties as primary 2003 Hawaii,Maui, Secretary ofAgriculture designates all Counties as primary disaster areas due Molokai,Oahu,Kauai to drought(2003);Governor proclaims statewide drought emergency. 2008- Statewide The first tune that D3(drought-extreme)had covered such a large area Present (percentage)ofthe State.The current drought is worse than the 2000-2002 drought. 14.3 Probability of Occurrence 14.3.1 Hazard Areas The impacts of drought can be categorized as economic, environmental, or social. Economic impacts can be observed as costs and losses to agricultural producers, costs and losses to livestock producers, and loss to the recreation and tourism industry. Environmental impacts can be categorized into damage to plant species, damage to animal species, and hydrological effects. Social impacts can be categorized as either health related, reduced quality of life and changes in lifestyle related, or even in increased conflicts regarding water use. Drought impact assessments begin by identifying direct consequences of the drought, such as reduced crop yields, livestock losses, and reservoir depletion. The risk of drought impact on the three sectors within the County of Hawaii is similar in terms of spatial variation. Most of the areas of concern are on the western side of the island, coinciding with low rainfall zones. What differs between each sector is the stage (moderate, 14-6 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts severe, or extreme) where drought risk may produce the most significant impacts. For the water supply sector, all stages produce significant risk on the western side of the island. The southern part of the island is also vulnerable to drought risk. The potential risk to this sector is clearly illustrated by applying the 12-month SPI. I ...:::....... water service Area Reservoirs Low Rain ::•...::::' ____= Medum Raub 140 Rain ..... -:C: Census Pop.Per Sq.We O.U27-0,126 0.705-2M72.34 Land Use DsW cis Agric t-L(A) j Conservation(C) y Rural(R) Urban(U) A 0 U 70 30 40 Mies w Figure 14-1. Drought Vulnerability to the water supply sector in the County of Hawaii In terms of the agriculture and commerce sector, again the western side of the island is at most risk, but the severe drought stage seems to coincide best with low rainfall areas on the west and southwest ends of the island, where various kinds of agricultural activities thrive. The use of a 3-month SPI shows well the potential risk to this sector. 14-7 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts i FGEM Uk"Systems '�l�: _ Far�nrtidl SVBarns 1 � �Alajcx Rosd5 i 1. '. ' IRa5-@fYUifS LSiVD Rgnculture Areas 1 how Rainfall Mednfrn RaInfafi `J High Rainfall No Data � hive Agneu flare Areas - Low Rarnfall Medium Ranfag r —1.High Rainfall No Data - I 0 1f 21 30 40 Miles E Figure 14-2. Drought Vulnerability to the agriculture sector in the County of Hawaii For the Pahoa area, droughts begin most frequently in July and December. For the Kea'au ar- ea, droughts begin most frequently in April-July and October-December. At the upper eleva- tions near the Volcanoes National Park, droughts begin most frequently in October-January, April, or June-July. Thus, island-wide droughts may begin any time of the year, and rainy pe- riods can end droughts any time of the year. This island is prone to the most intense droughts in the State. For frequency, the most drought-prone areas are the leeward areas such as South Kona and North Kohala. Current drought conditions are monitored nation-wide under a federal program involving several agencies,which produce a coded map. Tt currently shows portions of the leeward side of the island to be in an "extreme drought" condition, affecting both agriculture and water systems (see Figure 14-3). 14-8 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts August 18, 2009 U.S. Drought Vaid7amEST Hawaii Oro tCvndifrans f'eresnf Area) None D0-M 01-04 LU4N F � Curt 30-0 70.0 51.4 329 3.1 O.D LasMeek 121 87.9 55.4 33-9 3-1 OD p9i�120[•?r a71 3 Months Ago 02 9g.8 43.4 23.2 0.0 0.0 �05Q5QIIE map} SYart oY GaendarYear 21.1 78.E 5110 33-7 7-8 0.0 start of Water Year 1.6 98A 78.1 36.0 12.3 9.0 7 3!j7!2112 maps Dne Year Aga, 1-8 98A 5110 33.5 7-8 0.0 �MI9QCC2 map} BD D f ■t2 CrwgnL-sahame ::1 oraL]r--rfcder-e oa DrWgMt-Ercepucnar ::2 oraL]r--sevtrE- The Drnf:ght ritor facuses an bfoad-scale eondlliom. USDA Local conditraots may vary. See accompanvog text suraraarj, ���� for roreca.st statements. �". 4+Yny.urw`+u�,:..-. I$ Releaser!Thursday,August 20, 2009 http:!ldrought.unl.eduIdm Au froi:Laut'a Edwards, Western Regional Gfftnate GenrK Figure 14-3. Federal Drought Monitoring Map For wildfires, the State Division of Forestry and Wildlife (DOFAW) has the responsibility for the prevention and suppression of wildfires on State land and to cooperate with local agencies for the protection of wildlands on non-State land.68 To carry out this responsibility, DOFAW has identified areas where it has primary responsibility and would respond automatically, areas where it could respond mutually with other firefighting agencies upon request, and areas totally out of its jurisdiction but where DOFAW could nevertheless respond under specific conditions (e.g., extreme threats to public safety, local resources fully committed, extreme fire behavior). 14.4 Risk Assessment Currently there is no measure in place to quantify the potential economic impacts due to drought and corresponding wildfire events besides historical data. 68 Hawaii Revised Statutes,chapter 185(Land Fire Protection Law). 14-9 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts 14.5 Mitigation Strategies 14.5.1 Previous/Current Efforts Tt is known that a dry winter and possibly a dry spring in Hawaii usually follow the onset of El Nino. Given that the return period of El Nino is approximately three to five years, it would be useful to conduct a study to better anticipate drought patterns and severity in the future once an El Nino is developing. A similar study can be conducted for the La Nina events. None of the many rainfall-enhancement techniques tried have proven successful in practice. Better knowledge is needed on appropriate mitigation measures such as reservoir sizing that factors drought conditions, longer irrigation ditches, drought-resistant crops, low rainfall cul- tivation/tillage practices, changing planting to better areas during droughts, and designated emergency common areas to move cattle.69 The U.S. Department of Agriculture (USDA), with support from other agencies, maintains a drought mitigation center which assists states in developing drought mitigation plans. Hawaii is developing their plan under the State Water Commission. Crop insurance is available for mac nuts and some other primary local crops through the Co- operative Extension Service (CES), a program of the USDA and the University of Hawaii. This organization also provides information on drought-resistant plants and tillage. This section on droughts and wildfires would need to be updated in the future with findings from the ongoing study by the Hawaii Drought Committee.70 This study will identify drought and wildfire hazard areas and suggest mitigation actions. 69 Dr.A.D.Wall,Horticulturist,personal communication,October 2003. 70 Wilson Okamoto Corporation,County of Hawaii Drought Mitigation Strategies(Draft),prepared for the Ha- waii Drought Committee and State of Hawaii Commission on Water Resource Management,September 29, 2004. 14-10 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts 14.5.2 Future Plans Drought Mitigation Goals: • Expand current network of rain gages to improve rainfall monitoring. • Develop a framework to coordinate drought response between agencies. • Enhance current monitoring of ground- and surface-water levels. • Establish alert procedures for declining water level conditions. • Establish conservation programs to reduce water consumption. • Establish contingency water-hauling programs for livestock. • Seek authorization and funding for development of new water supply sources. • Identify areas at risk to drought and plan for regional response actions and strategies. • Develop additional storage and/or alternative sources of water supply. • Develop and implement drought-related public awareness programs. • Develop incentive programs for drought resistant practices. Project Description Status Drought/Wildland Fire Mitigation Plan County of Hawaii Unfunded Drought Mitigation Strategy 2004 Update Drought Monitor website; Maintenance Ongoing Update of Hawaii Rainfall Atlas:University of Hawaii,March 2012. Improvements to old plantation irrigation $30M Received partial FEMA system tunnels and ditches:Lower Hamakua funding Ditch System Renovations/improvements to old plantation $3M Proposed Project irrigation system tunnels and ditches:Kau Sugar System Reactivation Improvements to old plantation irrigation $26M Proposed Project system tunnels and ditches and new Kauahi reservoir:Waimea Improvements to the Kohala Ditch Irrigation Proposed Project: Post-earthquake repair Aqueduct Improvements to old plantation Ditch lining and/or closed completed irrigation transmission system. piping work still needs to L be done i Renovate and Reactivate old abandoned $2.5M Proposed Project plantation wells in Pahala Renovate and Reativate old Hamakua $100,000 Proposed Project Slaughterhouse well for non-potable agricultural use in Honokaa/Hamakua Construct new wells,surface water Investigation diversions,storage and transmission lines in priority areas Irrigating wisely: Promote better irrigation $100,000 Proposed Project practices and water management. Agricultural Water System for Kona, $25M in planning Honomalino: Provide a reliable source of water for agriculture and fire fighting assistance. Evaluate vulnerability ofCounty water $1M Completed si,stems and water trucking ca aci 14-11 Hawaii County Multi-Hazard Mitigation Plan Chapter 14:Hazard Analysis—Droughts Project Description Status Emergency Community Water Stations: Improve access to community water stations and develop additional stations for persons on catchment in priority areas. Dam&Reservoir Improvements Pun Waaivaa Reservoir Note:other post- Completed earthquake repairs are currently heing done%onapleted on HDWS, DHHL,and HDOA reservoirs Develop wells,storage,and construct $20M for 177 ranch lots This project is underway transmission systems for Puukapu encompassing 10,000 and will be completed acres Development and extension of domestic $10M Completed water transmission system for Kawaihae Extension of domestic water transmission Well,pump and tank system for Oceanview being completed;water spigot stations aDevelop wells,storage,and construct Needs planning study Need to establish Z. transmission systems for Puna improvement district to � finance this project. Makalei Water System Improvements: $5M Proposed 4-yr Project 3 Develop additional wells and reservoirs as well as upgrade the transmission system in the area from Keahole to Kailua-Kona for agricultural users. Various Water System Improvements within $50M Proposed 15-yr Project the County of Hawaii: Develop additional sources,storage facilities,as well as upgrade the transmission and distribution systems in high priority areas. 14-12 Hawaii County Multi-Hazard Mitigation Plan