Drought Mitigation Center Faculty Publications

Spatial Representation of Agroclimatology in a Study of Agricultural Drought

Olga Wilhelmi et al. — Fri, 12 Mar 2010 11:01:41 PST

Agricultural drought is the leading cause for crop failure throughout the world. In the USA, significant impacts of recent droughts on agricultural production indicate the continuing vulnerability of the country to drought. This paper presents a methodology for spatial representation of the agroclimatic component of agricultural drought vulnerability. This methodology was developed as a part of an integrated assessment of drought vulnerability. For the spatial analysis, the state of Nebraska was selected as a study area because of the considerable variation in climatology, soil characteristics, land use, and cropping patterns. The underlying approach assumes that the best spatial characterization of the state’s agroclimatology from the agricultural drought vulnerability perspective is the probability of seasonal crop moisture deficiency. Seasonal crop water-use thresholds for well-watered crops (e.g. corn, soybean, and sorghum) were estimated using the evapotranspiration (ET) mathematical model. For wheat and grass, ET values were estimated based on the relationship between ET, water-use efficiency, and crop yield. Historical grain yield data were analyzed to define an economically viable threshold for wheat. Seasonal ET thresholds determined for the crops were used to calculate area-weighted mean ET for the combination of crops in every county. The threshold values and long-term precipitation data were used for calculating statistical probabilities of seasonal crop moisture deficiency. Probability values were analyzed at 112 weather stations across Nebraska, spatially interpolated and classified using geographic information systems. The spatial pattern of probabilities of seasonal crop moisture deficiency reflected both seasonal precipitation across Nebraska and the distribution of crops and grasses.

Assessing Vulnerability to Agricultural Drought: A Nebraska Case Study

Olga V. Wilhelmi et al. — Fri, 12 Mar 2010 10:00:45 PST

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-irrigated cropland 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.

A Geospatial Decision Support System for Drought Risk Management

Steve Goddard et al. — Fri, 22 Jan 2010 12:25:30 PST

Drought affects virtually all regions of the world and results in significant economic, social, and environmental impacts. The Federal Emergency Management Agency estimates annual drought-related losses in the United States at $6-8 billion, which is more than any other natural hazard. Congress enacted the Agricultural Risk Protection Act of 2000 to encourage the United States Department of Agriculture (USDA) Risk Management Agency (RMA) and farmers to be more proactive in managing drought risk. Through the National Science Foundation (NSF) Digital Government program, the USDA RMA is working with the University of Nebraska−Lincoln Computer Science and Engineering (CSE) Department, National Drought Mitigation Center (NDMC), and High Plains Regional Climate Center (HPRCC) to develop new geospatial decision support tools to address agricultural drought hazards and identify regions of vulnerability in the management of drought risk. The goal of this research project is to develop a support system of geospatial analyses that will enhance drought risk assessment and exposure analysis. The tools and technologies developed have been integrated into the National Agricultural Decision Support System (NADSS), http://nadss.unl.edu/ .

An Operational Agricultural Drought Risk Assessment Model for Nebraska, USA

Hong Wu et al. — Tue, 11 Aug 2009 06:48:27 PDT

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.

Recent Advances in Drought Monitoring

Mark Svoboda et al. — Tue, 07 Jul 2009 09:46:35 PDT

Recent widespread, severe, and long-lasting droughts across North America have heightened awareness of and interest in how to better monitor drought and its impacts. Since its inception in 1999, the National Drought Mitigation Center (NDMC), United States Department of Agriculture (USDA) and NOAA’s Climate Prediction Center (CPC) and National Climatic Data Center (NCDC) have partnered to produce the weekly U.S. Drought Monitor (http://droug ht.unl.edu/m onitor/), a comprehensive drought assessment product based on a simple 5- category severity classification. On the heels of its widespread acceptance and usage, the NCDC, CPC, USDA, NDMC and scientists from Canada and Mexico have worked together to produce a monthly experimental North American Drought Monitor (http://www.ncdc.noaa.gov/oa/climate/monitoring/droug ht/nadm/index.html.
Other projects are underway. An informal interagency push toward better water resource assessment has a goal of developing a watershed-based hydrological drought map that would complement the weekly U.S. Drought Monitor map. The Western Governor’s Association and NOAA are developing a framework for a National Integrated Drought Information System. The NDMC is also involved in projects looking to improve our spatial and temporal capabilities in monitoring drought. By tapping into the Applied Climate Information System (ACIS), the NDMC has worked with UNL’s Computer Science and Engineering department and the High Plains Regional Climate Center (HPRCC) to develop a web-interface based tool, which allows the user to analyze drought indicators like the SPI, PDSI, and Newhall Soil Moisture Model.
A collaborative team of scientists from the USGS EROS Data Center, the NDMC, and the HPRCC is developing a prototype monitoring system that integrates information from climate and satellite databases using data mining techniques. The goal of this project is modeling the relationships between climate-based drought indicators and satellite-derived seasonal metrics from the NDVI (Normalized Difference Vegetation Index). This includes delivering near-real time information about drought-affected areas in the U.S. using the Internet as the primary delivery mechanism.
Clearly, the products and the cooperative efforts described above have advanced our drought monitoring capabilities and have led us to a better understanding of drought as a complex hazard while also improving our capacity to assess, predict and/or provide an early warning of drought.

Project Title: Sustainable Adaptations to Drought and Climate Variability in Agricultural Production Systems Across Nebraska

Cody L. Knutson et al. — Tue, 07 Jul 2009 09:43:39 PDT

Drought is a normal part of Nebraska’s climate. It is also the leading cause of monetary disaster loss in the United States. FEMA (1995) has estimated that U.S. drought losses average $6-8 billion dollars per year. A majority of these losses are incurred in the agricultural sector. Nebraska’s losses alone topped $1.2 billion in 2002 (AP 2003).
To enhance viable operations in this variable climate, many Nebraska farmers and ranchers have begun making the transition to agricultural practices that fall into the realm of sustainable agriculture. Sustainability has been increasingly stressed as essential for creating more resilient systems and reducing the effects of natural hazards (Anderson 1994, Mileti et al. 1995, Mehta 1997, United Nations 1997, Mileti 1999). However, little research has been done to understand the linkages between sustainable agriculture and drought management. This type of research is essential for enhancing agricultural adaptations to climate variability in Nebraska and in similar regions around the world.
This study focused on investigating the linkages between sustainable agriculture and drought within the state of Nebraska. Specifically, this research investigated coping mechanisms adopted by sustainable producers to reduce the effects of short and long-term drought, their perceived feasibility and effectiveness, and producer perceptions of drought and forecast products that are needed to increase the resiliency of sustainable agricultural systems to drought. This information was collected through a mail-back survey and in-depth interviews of Nebraska’s sustainable agriculture producers whom have had recent experience dealing with one of the most severe droughts in Nebraska’s recorded history.

Three Years and Counting: What’s New with the Drought Monitor

Mark D. Svoboda et al. — Tue, 07 Jul 2009 09:43:38 PDT

Operational since late summer 1999, the Drought Monitor (http://drought.unl.edu/monitor/) has refused to remain static. This unique weekly product attempts to make an assessment of current drought conditions in the contiguous United States, Hawaii, Alaska, and Puerto Rico. Four entities now share in authoring the map: the National Drought Mitigation Center (NDMC), Climate Prediction Center (CPC), United States Department of Agriculture (USDA), and National Climatic Data Center (NCDC).
The Drought Monitor effort has led to the development of new products and has reinforced the need for improvement and support of existing climate networks critical to monitoring our nation’s climate. One of the new products recognizes that drought has different short- and long-term characteristics. This product combines indicators representing the semi-independent nature of short- and long-term characteristics to improve drought monitoring. We are calling this family of products the experimental Objective Blends of Drought Indicators (OBDI).

Multiple-Year Droughts In Nebraska

Michael J. Hayes et al. — Tue, 07 Jul 2009 09:38:20 PDT

Most people understand that droughts have had a major impact on Nebraska in the past. Yet, many Nebraskans continue to be surprised when drought occurs. It is important to remember that droughts, including multiple-year droughts, are a normal part of Nebraska’s climate. This NebGuide discusses the history of drought in Nebraska, and aims to help Nebraskans better understand the range of climatic variability when they plan for drought.

Analysis of Time-Series MODIS 250 m Vegetation Index Data for Crop Classification in the U.S. Central Great Plains

Brian D. Wardlow et al. — Fri, 19 Jun 2009 09:31:16 PDT

The global environmental change research community requires improved and up-to-date land use/land cover (LULC) datasets at regional to global scales to support a variety of science and policy applications. Considerable strides have been made to improve large-area LULC datasets, but little emphasis has been placed on thematically detailed crop mapping, despite the considerable influence of management activities in the cropland sector on various environmental processes and the economy. Time-series MODIS 250 m Vegetation Index (VI) datasets hold considerable promise for largearea crop mapping in an agriculturally intensive region such as the U.S. Central Great Plains, given their global coverage, intermediate spatial resolution, high temporal resolution (16-day composite period), and cost-free status. However, the specific spectral–temporal information contained in these data has yet to be thoroughly explored and their applicability for large-area crop-related LULC classification is relatively unknown. The objective of this research was to investigate the general applicability of the time-series MODIS 250 m Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) datasets for crop-related LULC classification in this region. A combination of graphical and statistical analyses were performed on a 12-month time-series of MODIS EVI and NDVI data from more than 2000 cropped field sites across the U.S. state of Kansas. Both MODIS VI datasets were found to have sufficient spatial, spectral, and temporal resolutions to detect unique multi-temporal signatures for each of the region’s major crop types (alfalfa, corn, sorghum, soybeans, and winter wheat) and management practices (double crop, fallow, and irrigation). Each crop’s multi-temporal VI signature was consistent with its general phenological characteristics and most crop classes were spectrally separable at some point during the growing season. Regional intra-class VI signature variations were found for some crops across Kansas that reflected the state’s climate and planting time differences. The multi-temporal EVI and NDVI data tracked similar seasonal responses for all crops and were highly correlated across the growing season. However, differences between EVI and NDVI responses were most pronounced during the senescence phase of the growing season.

The Need for Integration of Drought Monitoring Tools for Proactive Food Security Management in Sub-Saharan Africa

Tsegaye Tadesse et al. — Tue, 05 May 2009 10:05:17 PDT

Reducing the impact of drought and famine remains a challenge in sub-Saharan Africa despite ongoing drought relief assistance in recent decades. This is because drought and famine are primarily addressed through a crisis management approach when a disaster occurs, rather than stressing preparedness and risk management. Moreover, drought planning and food security efforts have been hampered by a lack of integrated drought monitoring tools, inadequate early warning systems (EWS), and insufficient information flow within and between levels of government in many sub-Saharan countries. The integration of existing drought monitoring tools for sub-Saharan Africa is essential for improving food security systems to reduce the impacts of drought and famine on society in this region. A proactive approach emphasizing integration requires the collective use of multiple tools, which can be used to detect trends in food availability and provide early indicators at local, national, and regional scales on the likely occurrence of food crises. In addition, improving the ability to monitor and disseminate critical drought-related information using available modern technologies (e.g., satellites, computers, and modern communication techniques) may help trigger timely and appropriate preventive responses and, ultimately, contribute to food security and sustainable development in sub-Saharan Africa.