Natural Hazards: Droughts
Drought is a period recorded with less rainfall for a specific region compared to its past rainfall data, which might affect surface water flow, groundwater reserve, crop production and food availability. Impacts of a dry spell vary based on its duration as well as local people’s demand for food and water (National Drought Mitigation Center [NDMC], 2016). If the proportion of vulnerable population exposed to drought conditions were higher, then the impact of drought would also be high even if it lasted only for a short duration. In spite of being a natural hazard, the risk of its negative impacts largely depends on human activities. Population explosion, competition for land area, excess food demand, conversion of forests into agricultural lands and changes in land use pattern, increased storm water runoff due to reduced catchment areas, and several other anthropogenic causes amplify the impact of droughts.
Further, with climate change and global warming induced changes in the seasonal currents, extended periods of droughts would only become more common. Among other nations of the world US has been worst hit by frequent dry spells of large magnitude. From the “Dust Bowl” of 1935 to the recent 2015 drought in California, the states of USA are still refining their drought mitigation and disaster management plans. But, a comprehensive drought management framework can be established only if a thorough analysis of various climatological factors, and human activities that contributed to the widespread impacts of these droughts is carried out. Analyzing the reasons for incidence of droughts, their pattern and impacts would help in developing appropriate mitigation measures to better cope up with these natural hazards in future. This paper aims to analyze droughts and focus on existing drought mitigation plans adopted by states in US, as well as identify gaps in them and suggest improvements in drought adaptation strategies.
Analysis
Drought phenomenon has various definitions given by different disciplines. Meteorological drought is defined on the basis of degree of dryness experienced for certain duration. In US, meteorological drought is defined as less than 2.5mm rainfall in forty-eight hours (Whilhite and Glantz, 1985). Hydrologic drought is defined as a period in which stream flows are inadequate to supply intended water uses (Whilhite and Glantz, 1985). While meteorological drought definitions hold only for the specific country, hydrologic definitions are meant only for the particular river or water body with a given run-off rate. Agricultural drought is defined as a period in which the crop’s water demand is not met by the water availability, and socio-economic drought is defined as insufficiency in precipitation to meet established human activities or needs (Whilhite and Glantz, 1985). Thus defining drought is itself a complex task, as its impact on human life and environment is multifaceted. The “Dust Bowl” is the best example of a drought with disastrous consequences, and the recent aridity experienced in California is not less in its adversity either.
Dust Bowl 1930
Droughts are a common phenomenon in countries of the mid latitudes especially in North America. When, sea surface temperatures (SSTs) are lower than normal in eastern pacific due to the “La Nina” condition, and higher in the north Atlantic, the southern part of US has experienced severe droughts. However the “Dust Bowl” of 1930s differed from the La Nina induced drought pattern in its intensity as well as location. The 1930 drought atypically centered on the Great Plains instead of Mexico (Cook, Miller and Seager, 2008). Great Plains was transformed into a complete dessert, and black blizzards characterized the region during 1935. Drought combined with severe land misuse was the cause behind the self-perpetuating dust storms of 1930s (WGBH, 2013). Intensive farming and grazing during the period removed the grass layer that bound the topsoil, and the land remained exposed to intense dry conditions. Wind just blew away the soil leading to severe erosion. The entrapped dust prevented sun light penetration, and affected evapotranspiration as well as the water cycle severely. Thus, the dust perpetuated the dryness by interfering with the hydrological cycle, and the drought spread in its extent (Geggel, 2014). During the storms the visibility was reduced to less than a meter, and it affected normal life of people for months. Abandoning the region was the only way out (WGBH, 2013).
Long-term economical impact of the 1930 drought was a 17-30% decline in value of agricultural land in a span of 10 years between 1930 and 1940 (Hornbeck, 2012). The local governments tried to balance the agricultural losses through replanting programs that primarily focused on developing pastures and grasslands that are more resistant to erosion compared to croplands. But, the development continued to be slow in Great Plains, and the cost of “Dust Bowl’s” environmental destruction could only be economically balanced by the decline in population due to large-scale migration (Hornbeck, 2012). The drought of 1930’s thus projects how unplanned agricultural practices can magnify drought impacts to disastrous levels. Further, the “Dust Bowl” exemplifies the fact that complete recovery from a natural disaster is a very slow process that can take decades.
California Draught 2015
Atmospheric conditions similar to the winter of 1933, i.e. a “high pressure ridge in the west coast” deflecting storms and rainfall are also observed to be the reasons for the present drought conditions in California (Geggel, 2014). The La Nina effect is also contributing to the dryness. The dry spell that has started in 2010 progressed through 2015, and is still prevailing. On January 17th of 2014, California’s Governor declared a drought state of emergency. According to US Geological Survey (USGS), year 2014 was California’s driest year on record, and California’s surface as well as groundwater resources are dwindling (2015). The Shasta Lake reservoir in California, which had water up to 77% of its total capacity in 2011, was only at 27% of its capacity in 2014 and, the snow pack on the Sierra Nevada Mountains has also declined from 2011 to 2014 (USGS, 2015). These observations raise serious concerns about water availability in California, combined with the facts that there has been a population explosion in the last decade, and extreme tapping of groundwater (Romm, 2011).
While agricultural practices have been reformed since 1930, population growth induced pressure on natural resources has increased many folds. Climate change effects further help in creating several “Dust Bowl” like arid scenarios not just in US but all across the Globe, especially in the mid latitude countries. Given, that the atmospheric conditions favor frequent droughts, only the human influence on their intensification can be altered to reduce their adverse impacts.
Mitigation Measures
Drought mitigation starts from recognizing a shortfall in precipitation, and staying prepared beforehand. Drought is a crippling and slow moving disaster, but early warning and action can help in alleviating its impacts to a large extent. Drought mitigation thus includes rain and water resources monitoring, impact identification and risk assessment, planning mitigation measures, implementing the measures and reviewing them on a timely basis. Once a draught is predicted, farmers, ranchers, consumers from all sectors and landowners can plan accordingly, and reduce their water requirement.
The Colorado drought response plan is an apt example of a well-coordinated drought management plan that can be incorporated within the existing framework without the need for creation of a new government department. It comprises of an assessment system and a response system (McKee, Doesken and Kleist, 2000). The assessment system comprises of water availability task force (WATF), impact assessment task force, review and reporting task force. WATF regularly monitors and evaluates snow packs, reservoirs, rainfall, stream flow, groundwater levels, soil moisture and temperature for early drought signs. Once a drought condition is identified, its impacts are predicted, reports prepared and the response system immediately takes over (McKee, Doesken and Kleist, 2000). Impact task force carefully studies impacts all sectors including municipal water supply, agriculture, economic and energy, health, tourism, forest and wildlife. The response system includes lead agencies designated to handle the emergency (McKee, Doesken and Kleist, 2000). Thus, Colorado’s drought response plan is an effective model system that is being constantly reviewed and improved. Similar, drought response plans are used in several states across US, and California has adopted a science-based approach to drought mitigation incorporating regular assessment of water sources, land subsidence monitoring, energy and ecosystem health assessment, etc.
Simulation Models available today are valuable drought prediction tools, and they can be used to analyze reason behind historical droughts, predict similar conditions in future, and help in developing a management plan. Cook, Miller and Seager (2008), used modeling to understand why the “Dust Bowl” had a unique center, and more disastrous consequences compared to other droughts. Their simulation based on typical vegetation loss and atmospheric aerosol concentration that was present in the Great Plains during that time, clearly indicated that the normal “SST-forced drought pattern” was intensified by “human-induced land degradation” (Cook, Miller and Seager, 2008). Thus, using modeling one can simulate different scenarios, and predict the location, time and intensity of a drought, as well as predict the influence of human activities. Different mitigation measures can be applied in the model and the best option can be chosen based on the predicted impacts.
The US drought monitor tool developed by National Drought Mitigation Center (NDMC) provides required information to simulators in an interactive map form based on real-time data, statistical indices and reported impacts (2009). NDMC’s drought monitor is continuously being refined, and soon it would also include historic drought data for each region. This tool also incorporates meaningful indices such as the vegetation drought response index (VegDRI) and standardized precipitation index (SPI), derived from remote sensed satellite imagery. While VegDRI shows how crops and plants respond to drought, SPI gives drought information for a variety of time scales. Additionally, an impact reporter in the tool helps policy makers and researchers, access all historical drought impact reports (NDMC, 2009). On the whole NDMC provides valuable resources for simulating droughts, developing an efficient drought management plan, and developing “drought ready communities”.
Gaps in Drought Mitigation Plans
While the primary focus of countries is on predicting droughts, and water conservation, there is very less planning on managing future food demand, energy demand, and carbon emissions resulting from vegetation die-off during droughts, as well as human adaptation to prolonged droughts. As Romm (2011) points out, climate threatens the future of major food producers, and there is a need to plan to ensure food security to a growing world population. Both crops grown in the land and seafood are under threat, and this issue is not addressed in drought mitigation plans. Power generation requires water for cooling and when water is scarce, energy sector also would need to find new technological options. Carbon emissions from dying vegetation and wildfires would become more significant as drought incidences become more common, this would lead to further global warming and only worsen the situation.
The only adaptation to drought has been abandonment, migration and resettling of human population. This would lead to creation of more climate refugees, and the regions considered safe for habitation would be under severe stress due to heavy competition for resources. Thus, drought mitigation planning cannot be complete without a proper adaptation strategy. This strategy should incorporate aspects of water conservation, wastewater treatment recycling and reuse, cultivation of drought tolerant vegetation, proper maintenance of water bodies and watersheds with ample space for water seepage and replenishment of groundwater, etc. Further, the adaptation strategy should be implemented at the grassroots level, and the community should be well informed and prepared to face droughts without panic.
Summary of Findings (Conclusion)
Drought affects a large group of world population compared to any other natural hazard. Drought definition is complex, and its impacts also vary to a large extent on humans as well as different components of the environment. Human activities intensify the natural occurrence of dry conditions, and global climate change impacts would only increase the frequency of droughts in future. The world has to prepare itself for more “Dust Bowls”. But, with timely adoption of appropriate mitigation strategies the impacts can be reduced. Using techniques such as modeling and simulation, analyzing historical data and through better prediction, workable drought mitigation plans can be developed by government agencies. Regular monitoring of water sources, enforcing water conservation methods and preventing land encroachments can also help in enduring longer droughts with less trouble. However, there is a pressing need to identify ways to manage food insecurity and climate refugee issues, and incorporate them in drought management plans. Also, the drought management strategies need to be reviewed and modified from time to time based on the changing socio-economic as well as environmental conditions. Finally, widespread awareness about drought causes and impacts at the local level would create drought-ready communities that would handle these natural hazards more effectively. In a future drought prone world, negative impacts can still be kept minimal, if human activities are eco-responsive and sustainable.
References
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