The Science of Droughts

Literature Review on Drought: Types of drought (Metja et al., 2008)
Drought is a deficiency in precipitation over an extended period, usually a season or more, resulting in a water shortage causing adverse impacts on vegetation, animals, and people (NOAA, 2006). Precipitation is the primary factor controlling the incidence, formation and persistence of drought conditions, but evapotranspiration is also an important variable (Lloyd-Hughes and Saunders, 2002). Drought in South Africa is a very important phenomenon that affects not only agricultural production but also society. Some describe drought as a sustained and extensive occurrence of below average natural water availability, and can thus be characterized as a deviation from normal conditions of variables such as precipitation, soil moisture, groundwater and streamflow (Runtunuwu, 2005). It is a recurring and worldwide phenomenon, with spatial and temporal characteristics that vary significantly from one region to another (NOAA, 2006; Runtunuwu, 2005; Loukas and Vasiliades, 2004; Wilhelmi and Wilhite, 2002). Drought is a disastrous natural phenomenon that has significant impact on socio-economic, agricultural, and environmental spheres (Bhuiyan, 2004; Finan and Nelson, 2001; Loukas and Vasiliades, 2004). Its effects are recorded even in following periods when precipitation occurs normally. Damages due to drought depend on its intensity, duration, frequency and the affected area (Scripcariu et al., undated). This chapter provides a review of literature on drought. It starts by identifying different types of drought together with a focus on operational drought indices. It further focuses on the use of remote sensing in mapping and monitoring drought and the related satellite-derived drought indices. The chapter concludes by focusing on policy issues related to drought. (Read more)
White Paper: Monitoring Water in Extreme Droughts (Stu Hamilton)
Nothing focuses attention on the vital importance of water and the value of water monitoring as much an extended drought. The stakes are high. Every drop counts. Extreme droughts draw attention to shortcomings in our knowledge of exactly how much water is available at all points in the supply chain. As a result, droughts provide the best time to request public funding … for the much needed investments in water monitoring programs required to ll critical gaps in hydrological information. Additional funding for establishing new gauging stations and modernizing water monitoring capability enables the production of timely, accurate environmental insight. It enables the production of highly impactful water data that are relevant, reliable, and trustworthy (Read more).
A conceptual theoretical framework to integrally assess the possible impacts of climate change on domestic irrigation water use (Makwiza et al., 2015)
Domestic water use comprises indoor and outdoor components. Water is needed outdoors mainly for garden irrigation – to water vegetation such as lawns, flowerbeds and trees. Other outdoor water uses include pool top-ups, washing of cars, washing of hard surfaces, etc.. Water may also be used for small-scale urban agriculture – to grow edible plants like herbs, fruit and vegetables. Various climatic parameters impact outdoor water use, including, for example, rainfall, evapo-transpiration and ambient temperature (Balling et al., 2008; Praskievicz and Chang, 2009; Breyer and Chang, 2014). This climatically-driven water use profile is particularly true for edible plants with seasonal growth. (Read more)
Structure and precursors of the 1992/93 drought in KwaZulu-Natal, South Africa from NCEP reanalysis data (Dube and Jury, 2003)
As the demand for water increases in line with human population pressure and economic development activities, river ecosystems will continue to deteriorate unless they are managed in a sustainable way.  The main causes for this, particularly in their down-stream reaches, are related both to water quantity and water quality. The problem related to water quantity (e.g. the occurrence of extremely low flows) is governed by both natural events (drought) and human-induced factors (e.g. large upstream freshwater withdrawals).  Because it reduces the dilution capacity of the river, high levels of water withdrawal or loss from upstream river sections or tributaries can considerably affect the water quality of downstream river reaches. (Read more)
Hydrological simulation as a tool for agricultural drought assessment (Schulze, 1984)
That the intensity of the drought of the early 1980's has reached crisis proportions over many parts of Southern Africa is felt by rural and urban dweller alike. Irrigating time allotments have been curbed, farms dams have dried up, a succession of crop failures has placed severe demands on assistance to farmers by the State and urban water usage has been restricted by up to 50% (Read more).
Simulating drought in Southern Africa using sea surface temperature variations (Mason, Lindesay, and Tyson, 1994)
Changes in atmospheric circulation that produce droughts over South Africa are briefly reviewed, as too are the links between regions of homogeneous sea surface temperature variation in the oceans around Southern Africa and their correlation with rainfall over South Africa. Thereafter sea surface temperature anomaly fields known to be linked to the occurrence of droughts are used to initialise the 4-level CSIRO general circulation climate model to simulate drought over South Africa. Model results are compared with previously developed hypotheses concerning ocean-atmosphere interactions in the region and are shown to be consistent with observations in many important respects. (Read more)
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