Donald A. Wilhite

Understanding the drought phenomenon: the role of definitions

(1985). Understanding: the Drought Phenomenon: The Role of Definitions. Water International: Vol. 10, No. 3, pp. 111-120.

Monitoring the 1996 Drought Using the Standardized Precipitation Index

Abstract Droughts are difficult to detect and monitor. Drought indices, most commonly the Palmer Drought Severity Index (PDSI), have been used with limited success as operational drought monitoring tools and triggers for policy responses. Recently, a new index, the Standardized Precipitation Index (SPI), was developed to improve drought detection and monitoring capabilities. The SPI has several characteristics that are an improvement over previous indices, including its simplicity and temporal flexibility, that allow its application for water resources on all timescales. In this article, the 1996 drought in the southern plains and southwestern United States is examined using the SPI. A series of maps are used to illustrate how the SPI would have assisted in being able to detect the onset of the drought and monitor its progression. A case study investigating the drought in greater detail for Texas is also given. The SPI demonstrated that it is a tool that should be used operationally as part of a state, re...

Objective quantification of drought severity and duration

Common weaknesses of current drought indexes were analyzed. First, most of the current indexes are not precise enough in detecting the onset, end, and accumulated stress of drought. Second, they do not effectively take into account the aggravating effects of runoff and evapotranspiration, which build up with time. Third, they have a limited usefulness in monitoring ongoing drought because they are based on a monthly time step. Fourth, most of them fail to differentiate the effects of drought on surface and subsurface water supply. A new series of indexes are proposed to solve these weaknesses and to improve drought monitoring. In the new indexes, daily, rather than monthly, time steps are used. A new concept, effective precipitation (EP), the summed value of daily precipitation with a time-dependent reduction function, is proposed as a basic tool. Three additional indexes complement EP. The first index is each day’s mean of EP (MEP). This index shows climatological characteristics of precipitation as a water resource for a station or area. The second index is the deviation of EP (DEP) from the MEP. The third index is the standardized value of DEP (SEP). By using these three indexes, consecutive days of negative SEP, which can show the onset, the ending date, and the duration of a water deficit period is categorized. With the duration categorized, four additional indexes that can show drought severity are calculated: 1) accumulation of consecutive negative SEP, which shows the duration and severity of precipitation deficit together ; 2) accumulated precipitation deficit, which shows precipitation departure from the normal during a defined period; 3) precipitation for the return to normal; and 4) effective drought index, a standardized index that can be used to assess drought severity worldwide. The merits and weaknesses of each index are compared. New quantified definitions on drought and its onset, end, and duration are proposed. These indexes were tested in the High Plains region of the United States from 1960 to 1996. The results were compared to historical reports of drought. From this analysis, it was concluded that the new indexes not only advanced objectivity, but also offered a number of advantages in practical use. These are 1) a more precise determination of drought duration, 2) the usefulness in monitoring an ongoing drought, and 3) the variety of ways a drought’s characteristics can be described.

Assessing Vulnerability to Agricultural Drought: A Nebraska Case Study

Recent drought events in the United States and the magnitude of drought losses indicate the continuing vulnerability of the country to drought. Until recently, drought management in many states, including Nebraska, has been largely response oriented with little or no attention to mitigation and preparedness. In 1998, Nebraska began to revise its drought plan in order to place more emphasis on mitigation. One of the main aspects of drought mitigation and planning is the assessment of who and what is vulnerable and why. This paper presents a method for spatial, Geographic Information Systems-based assessment of agricultural drought vulnerability in Nebraska. It was hypothesized that the key biophysical and social factors that define agricultural drought vulnerability were climate, soils, land use, and access to irrigation. The framework for derivation of an agricultural drought vulnerability map was created through development of a numerical weighting scheme to evaluate the drought potential of the classes within each factor. The results indicate that the most vulnerable areas to agricultural drought were non-irrigatedcropland and rangeland on sandy soils, located in areas with a very high probability of seasonal crop moisture deficiency. The identification of drought vulnerability is an essential step in addressing the issue of drought vulnerability in the state and can lead to mitigation-oriented drought management.

Drought and Water Crises : Science, Technology, and Management Issues

OVERVIEW Drought as Hazard: Understanding the Natural and Social Context, Donald A. Wilhite and Margie Buchanan-Smith DROUGHT AND WATER MANAGEMENT: THE ROLE OF SCIENCE AND TECHNOLOGY The Challenge of Climate Prediction in Mitigating Drought Impacts, Neville Nicholls, Michael J. Coughlan, and Karl Monnik Drought Monitoring: New Tools for the 21st Century, Michael J. Hayes, Mark Svoboda, Douglas Le Comte, Kelly T. Redmond, and Phil Pasteris Drought Indicators and Triggers, Anne C. Steinemann, Michael J. Hayes, and Luiz F. N. Cavalcanti Drought Preparedness Planning: Building Institutional Capacity, Donald A. Wilhite, Michael J. Hayes, and Cody L. Knutson National Drought Policy: Lessons Learned from Australia, South Africa, and the United States, Donald A. Wilhite, Linda Botterill, and Karl Monnik Managing Demand: Water Conservation as a Drought Mitigation Tool, Amy Vickers The Role of Water Harvesting and Supplemental Irrigation in Coping with Water Scarcity and Drought in the Dry Areas, Theib Y. Oweis Drought, Climate Change, and Vulnerability: The Role of Science and Technology in a Multi-Scale, Multi-Stressor World, Colin Polsky and David W. Cash CASE STUDIES IN DROUGHT AND WATER MANAGEMENT: THE ROLE OF SCIENCE AND TECHNOLOGY The Hardest Working River: Drought and Critical Water Problems in the Colorado River Basin, Roger S. Pulwarty, Katherine L. Jacobs, and Randall M. Dole Drought Risk Management in Canada-U.S. Transboundary Watersheds: Now and in the Future, Grace Koshida, Marianne Alden, Stewart J. Cohen, Robert A. Halliday, Linda D. Mortsch, Virginia Wittrock, and Abdel R. Maarouf Drought and Water Management: Can China Meet Future Demand? Zhang Hai Lun, Ke Li Dan, and Zhang Shi Fa A Role for Streamflow Forecasting in Managing Risk Associated with Drought and Other Water Crises, Susan Cuddy, Rebecca Letcher, Francis H. S. Chiew, Blaire E. Nancarrow, and Tony Jakeman Droughts and Water Stress Situations in Spain, Manuel Menendez Prieto INTEGRATION AND CONCLUSIONS Drought and Water Crises: Lessons Learned and the Road Ahead, Donald A. Wilhite and Roger S. Pulwarty Index

Drought assessment, management, and planning: theory and case studies.

Preface. Part One: Theory. 1. The Enigma of Drought D.A. Wilhite. 2. Monitoring Regional Drought Conditions K.G. Hubbard. 3. The Role of NOAA Satellite Data in Drought Early Warning and Monitoring: Selected Case Studies G.E. Johnson, V. Rao Achutuni, S. Thiruvengadachari, F. Kogan. 4. Assessing the Regional Consequences of Drought: Putting the MINK Methodology to Work on Todays Problems W.E. Easterling. 5. Agricultural Drought Management Strategies to Alleviate Impacts: Examples from the Arid and Subhumid Regions of the Indian Subcontinent A.S.R.A.S. Sastri. 6. Planning for Drought: a Methodology D.A. Wilhite. 7. Implications of Global Warming for Climate Variability and the Occurrence of Extreme Climate Events L.O. Mearns. Part Two: Case Studies. 8. Drought Risk and Water Management in Israel: Planning for the Future H.J. Bruins. 9. Indian Drought Management: from Vulnerability to Resilience A.R. Subbiah. 10. Drought and Policy Responses in the Brazilian Northeast A. Rocha Magalhaes. 11. Drought Policy in the Republic of South Africa J.J. Bruwer. 12. Drought in Australia: Prediction, Monitoring, Management, and Policy D. White, D. Collins, M. Howden. 13. Drought Mitigation in the United States: Progress by State Government D.A. Wilhite, S.L. Rhodes. 14. Institutional Responses to the 1987-92 California Drought J. Rich. 15. Drought in China: Present Impacts and Future Needs Kerang Li, Xianchao Lin. Index.

An Operational Agricultural Drought Risk Assessment Model for Nebraska, USA

Drought is a common occurrence in Nebraska and agriculture is the primary economic sector affected. Because of repeated and widespread severe drought impacts, more emphasis on drought risk management is warranted. This study develops an agricultural drought risk assessment model using multivariate techniques. The model is specific to corn and soybeans and is able to assess real-time agricultural drought risk associated with crop yield losses at critical phenological stages prior to and during the growing season. The assessment results are presented in a Geographic Information System to provide a better visualization. This model provides information in a timely manner about potential agricultural drought risks on dryland crop yield to decision makers ranging from agricultural producers to policy makers from local to national levels.

A methodology for drought preparedness

Drought is a normal, recurrent feature of climate that affects virtually all countries to some degree. The number of drought-induced natural disasters has grown significantly since the 1960s, largely as a result of increasing vulnerability to extended periods of precipitation deficiency rather than because of an increase in the frequency of meteorological droughts. This increase in drought-induced natural disasters has resulted in a considerable growth of interest in drought mitigation and preparedness worldwide. The purpose of a national preparedness plan is to reduce societal vulnerability to drought through the adoption of preventive, anticipatory policies and programs. This paper describes a ten-step planning process that nations can follow to develop a drought preparedness plan. This process, originally developed in 1987, has been the basis of discussions at training seminars on drought preparedness for developing nations in Africa, Asia, and Latin America. It has also been adopted, with appropriate modifications, by state or provincial governments and by municipalities. The process is intended to be flexible so that governments can add, delete, or modify the suggested steps, as necessary.

Improving Federal Response to Drought

Abstract Severe and widespread drought occurred over a large portion of the United States between 1974 and 1977. Impacts on agriculture and other industries, as well as local water supplies, were substantial. The federal government responded with forty assistance programs administered by sixteen federal agencies. Assistance was provided primarily in the form of loans and grants to people, businesses and governments experiencing hardship caused by drought. The total cost of the program is estimated at

The Enigma of Drought

7–8 billion. Federal response to the mid-1970s drought was largely untimely, ineffective and poorly coordinated. Four recommendations are offered that, if implemented, would improve future drought assessment and response efforts: 1) reliable and timely informational products and dissemination plans; 2) improved impact assessment techniques, especially in the agricultural sector, for use by government to identify periods of enhanced risk and to trigger assistance measures; 3) administratively centralized drou...