GNR 639 GNR 639 : Natural Disaster And Management Lesson 9 Drought Prof. R. Nagarajan, CSRE , IIT Bombay 9.01
GNR 639 GNR 639 : Natural Disaster And Management Water stress occurs when the demand for water exceeds the available amount during a certain period or when poor quality restricts its use. Falkenmark Water Stress Indicator - a country or region is said to experience "water stress" when annual water supplies drop below 1,700 cubic metres per person per year. At levels between 1,700 and 1,000 cubic metres per person per year, periodic or limited water shortages can be expected. When water supplies drop below 1,000 cubic metres per person per year, the country faces water scarcity. Water crisis is a general term used to describe a situation where the available water within a region is less than the region's demand (potable water). Drought is a period of drier-than-normal conditions that results in water-related problems, when rainfall is less than normal for several weeks, months or years, the flow of streams and rivers declines and water levels in lakes and reservoirs fall and the depth to water in wells increase. Famine results from a sequence of processes and events that reduces the food availability and causes widespread and increased morbidity and mortality. Prof. R. Nagarajan, CSRE , IIT Bombay 9.02
GNR 639 GNR 639 : Natural Disaster And Management GLOBAL WATER AVAILABILITY • 70% Earth Surface covered with water • Total water reserves: 1400 m km3 • 97.5% Water is salty • 2.5% Water is fresh (35 m km3) Out of total fresh water - 68.7%% is frozen in ice caps 30% is ground water 0.3% is surface water (Lakes 87%, swamp 11% and river 2%) • Only 1% (0.007% of total water) is useable WASTAGE OF WATER • Only 35% rain water is used effectively • Heavy soil erosion along river banks is causing floods and forcing rivers to change their direction • 40 m ha flood prone; 8 -10 m ha affected every year: Floods in 2007-08 caused 3659 deaths, loss of 0.114 m livestock and damaged 3.5 m houses • 70% Irrigation water, 48% river water wasted • Flood irrigation turning agriculture expensive • 20 m wells pumping water with free power, resulting in depletion of ground water and intrusion of sea water in coastal areas Prof. R. Nagarajan, CSRE , IIT Bombay 9.03
GNR 639 GNR 639 : Natural Disaster And Management Water Scarcity – 2025 Outlines show those that are both in and approaching scarcity Prof. R. Nagarajan, CSRE , IIT Bombay 9.04
GNR 639 GNR 639 : Natural Disaster And Management Drought situations develop due to: • Deficit precipitation that yield required volume of water • Storage systems do not have sufficient water for supply • Lesser crop area to meet food requirements • Sale in distress conditions • Crisis management approach is used in Drought management • Resources & risk based capacity management practices • Climate scenario along with depleted resources need • Alternate sources of supply drain out on continuous tapping • Need for inherent resource management based on vulnerability • Exposure, sensitivity, adoptive capabilities Prof. R. Nagarajan, CSRE , IIT Bombay 9.05
GNR 639 GNR 639 : Natural Disaster And Management Drought is a period of drier-than-normal conditions that results in water-related problems, when rainfall is less than normal for several weeks, months or years, the flow of streams and rivers declines and water levels in lakes and reservoirs fall and the depth to water in wells increase. If dry weather persists and water-supply problem develops, the dry period can become a drought. Famine results from a sequence of processes and events that reduces the food availability and causes widespread and increased morbidity and mortality. It has occurred periodically in the history. In Chronicles of ancient civilization in India, Egypt, Western Asia, China, Greece and Rome, had recorded famines. Desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. It is also defined as areas with an average annual precipitation of less than 250 mm per year. Desertification is the process of destruction of the biological potential of the land and can lead ultimately to widespread deterioration of ecosystem. It is the means of conversion of a fertile land towards a dry infertile or deserted land 9.06 Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 639 GNR 639 : Natural Disaster And Management Drought ranges from - statistical (the lowest decile of annual rainfall) to a meteorologist; through yield being limited by too little water to an agronomist; shortfall in the storage system and distribution curtailments to water resources engineers . farmer, it corresponds to management issues, such as - how best to manage a meteorologically drought-prone farm over several years, Permanent - characteristics of the driest climate, and drought vegetation is found and the agriculture is possible only by irrigation Seasonal – planting dates and the crop duration should be synchronized with rainy season and residual moisture storage (arid and semi-arid regions) Contingent - irregular occurrence and there is no regular season of occurrence and invisible -occurs even when there is frequent rainfall and occurs in humid region by Thornwaite (1947). 9.07 Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 639 GNR 639 : Natural Disaster And Management Absolute drought is a period of at least 15 consecutive days to, none of which is credited 0.01 inches of rain or more. Partial drought is a period of at least 29 consecutive days, the mean daily rainfall of which does not exceed 0.01 inches. Dry spell is a period of no rain condition for at least 15 consecutive days to none, out of which 0.04 inches or more is credited for the period. Meteorological drought is the deficiency of rainfall compared to the average mean annual rainfall of an area. Agriculture drought is related to the reduced topsoil moisture at planting stage that may hinder germination, leading to lesser plant population per hectare and a reduction of final yield. It is grouped into - Early season (Delayed onset, prolonged dry spells after onset of monsoon), Mid-season (Inadequate soil moisture between two rain events) and late season (Early cessation of rains or insufficient rains). Prof. R. Nagarajan, CSRE , IIT Bombay 9.08
GNR 639 GNR 639 : Natural Disaster And Management Hydrological drought is associated with shortfalls on surface or subsurface water supply for established water uses of a given water resources management system on a watershed or river basin scale. It takes longer for precipitation deficiencies to show up in components of the hydrological system such as soil moisture, stream flow, and ground water and reservoir levels. Socio-economic drought is associated with failure of water resources systems to meet water demands and thus associating droughts to meet water demands and thus associating droughts with supply of and demand for an economic good ( 9.09 Prof. R. Nagarajan, CSRE , IIT Bombay
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.10
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.11
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.12
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.13
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.14
GNR 639 GNR 639 : Natural Disaster And Management Prof. R. Nagarajan, CSRE , IIT Bombay 9.15
GNR 639 GNR 639 : Natural Disaster And Management Factors responsible for drought are • ocean – atmosphere system, sea surface temperature anomalies, high temperature of the soil during drought and the increase in fine particles in the air, the high albedo in dry areas • solar-weather relationship • monsoon mechanism and impairment of this mechanism. Prof. R. Nagarajan, CSRE , IIT Bombay 9.16
GNR 639 GNR 639 : Natural Disaster And Management Common consequences of drought include: 1) Diminished crop growth or yield productions and carrying capacity for livestock; 2) Dust storms when drought hits an area suffering from desertification and erosion; 3) Famine due to lack of water for irrigation; 4) Habitat damage, affecting both terrestrial and aquatic wildlife; 5) Malnutrition, dehydration and related diseases; 6) mass migration resulting internal displacement and international refugees; 7) reduced electricity production due to reduced water flow through hydroelectric dam; 8) Shortages of water for industrial users; 9) civil restlessness or war over natural resources – water and food, 10) wild fires / bush fires are common during drought times. 9.17 Prof. R. Nagarajan, CSRE , IIT Bombay
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