eChapters

Drought is a situation when the demand for water is much greater than the availability of water. Drought is a creeping phenomenon and it is experienced only after it has set in. The scarcity of water compared to demand will have greater impact on every activity of human life including failure of crops, food shortages, decline in ground water table, drying tanks, lakes or reservoirs, acute shortage of drinking water for humans and livestock shortage for cattle etc.

Drought will have very serious impact on economy of households as well as that of nation. There are five different types of droughts depending upon the nature of shortage of water

10.1 Meteorological Drought

Meteorological drought occurs when the water received through rainfall during a given period is much less than long period average rainfall of the area. The meteorological drought is associated with either failure of rain or due to long gap between the successive rainfall events. In India, meteorological drought occurs due to failure of south west monsoon or long breaks in south west monsoon rainfall. In Tamil Nadu the drought occurs due to failure of north east monsoon rainfall during months of October to December.

The division of earth’s climates into worldwide system of contiguous regions, each one of which is defined by relative homogeneity of the climatic elements (Fig. 9.1)

9.1 Koppen’s Classification

Koppen’s climatic classification describes 5 major groups of climate A, B, C, D and E which are sub-divided into a total of 14 individual climate types, along with a special category of Highland (H) climate.

A - Tropical: Average temperature of coldest month is 18°C or more.

B - Dry climate: Potential evapotranspiration exceeds precipitation.

C - Warm temperature: The average temperature of the coldest month (of the middle latitudes) is higher than -3°C but below 18°C.

The general circulation of the atmosphere explains the formation of pressure belts and wind systems in the earth’s atmosphere. It is known that the earth receives more solar radiation near the equator and gets heated more. Consequently, the air gets heated more and rises vertically upwards. As there is more convection of the air near the equator, the atmospheric pressure will be less. The warm air which moves upwards up to a height about 14 km near the equator gets cooled and move towards the poles.

The upper air gets gradually cooled when it reaches a latitude of 30°N in the northern hemisphere and 30°S in the southern hemisphere. At about 30°latitude the cold air descends to the earth’s surface. Some of the cold air after descending to earth’s surface moves towards the equator. The circulation of air between the equator and 30°N or 30°S latitudes is called Hadley cells (Fig. 8.1).

The winds blowing from 30° latitude towards the equator at surface level are called trade winds. These trade winds which move towards the equator in both northern hemisphere and southern hemisphere converge near the equator and the zone of the convergence of these winds is called Inter Tropical Zone of Convergence. As the convergence of air takes place, due to convection of heat as a result of high temperatures leads to vertical lifting of moist air. Therefore, the Equatorial regions receive more rainfall and there are tropical forests in this region.

Clouds play very important role on weather and climate. The formation of clouds takes place when water condenses in the sky. Clouds are visible accumulation of tiny water droplets and ice crystals in the Earth’s atmosphere. The moisture is always present in the atmosphere though it may not be visible. Clouds form when air becomes cooler until the water vapour present in it condenses to liquid form. The condensation over oceans occurs around solid particles like salt, dust, smoke etc. suspended in the atmosphere. The type of clouds depends upon temperature and wind. The clouds are classified based on physical appearance and the height at which clouds are formed (Fig. 7.1).

Clouds play very important role on weather and climate. The formation of clouds takes place when water condenses in the sky. Clouds are visible accumulation of tiny water droplets and ice crystals in the Earth’s atmosphere. The moisture is always present in the atmosphere though it may not be visible. Clouds form when air becomes cooler until the water vapour present in it condenses to liquid form. The condensation over oceans occurs around solid particles like salt, dust, smoke etc. suspended in the atmosphere. The type of clouds depends upon temperature and wind. The clouds are classified based on physical appearance and the height at which clouds are formed (Fig. 7.1).

The mass of a body is usually defined as the material content of the body whereas the weight of the body is defined as the force with which the body is attracted towards the earth due to gravity. Therefore, the weight of a body is the product of its mass and acceleration due to gravity. The air in the atmosphere, which is a mixture of several gases has certain mass and although not very dense, will acquire some weight due to gravitational force of attraction when the entire column of the atmosphere from the ground level to the top of it is considered. Pressure is defined as the force for unit area. Therefore, the atmospheric pressure is defined as the force exerted by an air column of units area of cross section extending from earth’s surface to the top of atmosphere. As we go up in the atmosphere the height of the air column decreases, the air also become rarer and the atmospheric pressure decreases with increase in height.

In meteorology, temperature is always referred to as the temperature of the air unless it is stated otherwise. There will always be exchange of heat in the atmosphere from a point at high temperature to a point at lower temperature. The transfer of heat through convection and radiation is always observed in the atmosphere whereas the conduction of heat takes place near the earth’s surface.

4.1 Diffusion of Heat

Heat diffuses (spreads) at different rates through different media, the rate at which diffusion of heat takes place is called thermal diffusivity. The thermal diffusinty of of some selected materials is given below:

One can see from the above table that iron has got higher diffusivity compared to wood. Suppose one end of iron rod is kept at hot temperature, the heat spreads faster in iron rod and the other end gets warmer quicker than in the case of a wooden stick which means that the transfer of heat is quicker in bodies with higher thermal diffusivity.

Three fundamental processes that are responsible for inducing changes in weather are transfer of heat, energy and mass. The Sun, whose inter-surface temperature is estimated to be around 6000°C emits heat energy in the form of solar radiation which is received at the earth’s surface after it is partly depleted in the atmosphere. Therefore, it is essential to understand the processes that govern the transfer of heat in the earth-atmosphere system.

3.1 Conduction

The transfer of heat from one point to another point within the material medium without the actual movement of the particles in the medium is called conduction i.e. the heat energy transfer is conducted by the particles in the medium from hot end to cold end. If a metal rod is heated at one end, the other end of rod becomes hot gradually due to transfer of heat by conduction. In the earth atmosphere system, conduction of heat is observed at the ground surface only. The amount of heat energy transferred due to conduction (Q) is

Air is one of the primary things that make life on earth possible. The earth’s atmosphere or air is made up of variety of gases and other particles. The dynamic layer surrounding the earth’s surface containing various mixture of gases, moisture and solid particles (aerosols) is called atmosphere. The atmosphere is generally defined as the gaseous envelop surrounding the earth.

The formation of the earth was believed to be about five billion years ago. In the first 500 million years, a thick atmosphere emerged from the vapour and gases that were expelled from the interior of the earth. Hydrogen (H2 ), water vapour, methane and carbon dioxide were some of the gases believed to be initially formed in the atmosphere due to out gassing from the interior of the earth. About 3.5 billion years ago, the atmosphere consisted of carbon dioxide (CO2 ), Carbon monoxide (CO), water vapour (H2 O), nitrogen (N2 ) and hydrogen present in atmospheric layers like troposphere, stratosphere, mesosphere, thermosphere (Fig. 2.1). The condensation of water vapour into water led to the formation of oceans in which sedimentation occurred and the hydrosphere was created. In the initial and ancient environment, oxygen was not present. Anaerobic is technical word which literally means without air (where air is generally used to mean oxygen and aerobic indicates the presence of oxygen). Evidence of such an anaerobic reducing atmosphere was hidden in early rock formations such as iron and uranium in their reduced states.

Aristotle (384 to 322 BC), an ancient Greek philosopher and scientist (Fig. 1.1) developed the concept of meteorology as a study of the lower atmosphere. Over the years meteorology developed as a science of atmosphere which deals with the physics, dynamics and chemistry of the atmosphere and their effect upon the earth’s surface, oceans and thereby life in general either directly or indirectly.

As the atmospheric conditions change from time to time in a given area and from place to place in a given time, climatology was developed as a science which studies the average conditions of the weather and its variability over a long period of time.

All most all the human activities are greatly influenced by the weather and climate to a greater extent. Therefore, the scope of meteorology encompasses various activities which are of considerable economic significance as detailed here below;

1.1 Housing

The design and construction of houses, buildings, industrial structures etc. depends upon the weather and climate of the region. Orientation of doors, windows roofs of the buildings are usually designed to provide maximum comfort and convenience to the people.

6.1 Introduction to Remote Sensing in Watershed Management

Remote sensing involves acquiring information about the Earth's surface without physical contact, using satellite or aerial imagery. This technology has revolutionized watershed management by providing detailed and timely data, crucial for effective planning and decision-making.

6.2 Remote Sensing Technologies and Techniques

Satellite Imagery

Satellite imagery involves capturing images of the Earth from space using satellites equipped with sensors. Some of the most notable satellite missions providing high-resolution imagery for large-scale environmental monitoring include Landsat, Sentinel, and MODIS.

a. Landsat: Operated by NASA and the US Geological Survey, Landsat satellites have been observing the Earth since 1972. Landsat provides medium-resolution images (15-60 meters per pixel) in both visible and infrared wavelengths, allowing for detailed monitoring of land use, vegetation health, and water bodies.

5.1 Participatory Approaches to Watershed Management

Community Engagement Strategies: Exploring methods for involving local communities in decision-making processes, project planning, and implementation, including participatory rural appraisal (PRA), stakeholder consultations, and community meetings. Exploring methods for involving local communities in decision-making processes, project planning, and implementation is essential for promoting ownership, sustainability, and effectiveness of development initiatives within watershed areas. Here are key community engagement strategies:

a. Participatory Rural Appraisal (PRA): PRA is a participatory approach that involves community members in assessing their own needs, priorities, resources, and capacities. PRA techniques, such as transect walks, social mapping, seasonal calendars, and wealth ranking, enable communities to identify and analyze local issues, strengths, and opportunities. PRA fosters dialogue, builds trust, and empowers communities to take ownership of development processes.

b. Stakeholder Consultations: Conduct stakeholder consultations to engage a diverse range of actors, including community members, local leaders, government officials, civil society organizations, and other stakeholders. Consultations provide opportunities for stakeholders to share their perspectives, knowledge, and concerns, and contribute to decision-making and project design. Stakeholder consultations ensure inclusivity, transparency, and legitimacy in development processes.

c. Community Meetings: Organize community meetings, village assemblies, or public forums to facilitate dialogue, consensus-building, and decision-making among community members. Community meetings provide platforms for discussing development priorities, reviewing project progress, and resolving conflicts collaboratively. They foster social cohesion, collective action, and community mobilization around shared goals and aspirations.

4.1 Demographic Profile of Watershed Communities

• Population Distribution: Examining the spatial distribution and density of population within watershed areas, including rural settlements, urban centers, and peri-urban zones. Analyzing population distribution within watershed areas involves understanding how people are distributed across various types of settlements, including rural, urban, and peri urban zones. Here's a breakdown of each:

a. Rural Settlements: These are typically smaller communities dispersed throughout the watershed area, often engaged in agriculture, forestry, or other primary industries. Population density in rural areas tends to be lower compared to urban centers. The distribution of rural settlements can be influenced by factors such as terrain, availability of natural resources, and historical land use patterns.

b. Urban Centers: Urban areas within watershed boundaries consist of cities and towns with higher population densities and more developed infrastructure. These areas are characterized by a concentration of economic activities, services, and amenities. Population distribution within urban centers can vary widely, with some areas experiencing high population density in downtown cores and others having more spread-out suburbs.

3.1 Land Use and Land Cover Analysis

Concept and Importance: Understanding the significance of land use and land cover analysis in watershed management for assessing spatial patterns of human activities and natural ecosystems.

Land use and land cover analysis is a fundamental tool in watershed management, providing valuable insights into the spatial patterns of human activities and natural ecosystems within watersheds. Here's an exploration of the concept and importance of land use and land cover analysis in watershed management:

a. Concept: Land use refers to the human activities and practices conducted on the land, including residential, commercial, industrial, agricultural, recreational, and conservation activities. Land cover, on the other hand, refers to the physical and biological features of the land surface, including vegetation, water bodies, bare soil, impervious surfaces, and artificial structures. Land use and land cover analysis involves mapping, classifying, and quantifying the spatial distribution and temporal changes of different land use and land cover types within watersheds using remote sensing, Geographic Information Systems (GIS), and field surveys.

b. Significance: Land use and land cover analysis is essential for watershed management due to its significance in understanding the interactions between human activities and natural processes, assessing environmental impacts, and guiding land management decisions. Key reasons for the importance of land use and land cover analysis in watershed management include:

2.1 Definition and Boundaries of Watershed Areas

Concept of Watershed Boundaries

The concept of watershed boundaries is fundamental to understanding the hydrological and ecological dynamics of a given landscape. Watershed boundaries, also known as drainage divides or catchment areas, delineate the geographical extent of a watershed, which is an area of land where all the water drains to a common outlet, such as a stream, river, lake, or ocean. Watershed boundaries represent the natural hydrological and ecological units of a landscape, reflecting the interconnectedness of water resources and ecosystems. Understanding the factors influencing their definition is essential for effective watershed management, resource planning, and environmental conservation. Exploring the delineation of watershed boundaries involves considering various factors that influence their definition:

a. Topography: Topography, particularly the elevation and slope of the land, plays a significant role in defining watershed boundaries. Watershed boundaries typically follow ridgelines or high points in the landscape, where water flows in different directions, ultimately converging into distinct drainage networks.

b. Hydrology: Hydrological characteristics, such as precipitation patterns, surface runoff, and groundwater flow, influence the delineation of watershed boundaries. Areas with higher rainfall or snowmelt may have larger watersheds with more extensive drainage areas, while areas with low precipitation may have smaller, more localized watersheds.

1.1 Introduction to Integrated Watershed Management

Definition and Scope of Integrated Watershed Management: Integrated Watershed Management (IWM) refers to a comprehensive approach to managing the resources and ecological processes within a watershed area in a coordinated and integrated manner. Integrated watershed management represents a holistic approach to managing natural resources within a watershed, with the aim of achieving sustainable development while maintaining ecosystem health and resilience. It involves collaboration among various stakeholders and integrates scientific knowledge with traditional wisdom to address complex environmental challenges. This section aims to provide a clear understanding of what integrated watershed management entails, including its scope and key components.

a. Definition of Integrated Watershed Management: Integrated Watershed Management is a holistic and multi-disciplinary approach that considers the entire watershed as a unit for planning and managing natural resources. It involves the coordinated management of land, water, vegetation, and other resources within a watershed to achieve sustainable development goals while preserving ecological integrity.

Introduction

Agriculture is the backbone of every country. It largely depends on climate and its changes. Over the last few years climate change has affected crops, cropping systems, patterns and the ecosystem hugely. Climate change is caused by greenhouse gases in the atmosphere, which results in global warming (Aydinalp and Cresser, 2008). The rising temperature, melting of glaciers, loss in vegetation cover, frequent occurrences of drought and floods are some of the issues that have raised concern among the environmentalists. The change in temperature and precipitation patterns alters the traditional growing seasons. Climate change is expected to influence crop and livestock production, hydrologic balances, input supplies and other components of agricultural systems (Adams et. al., 1998). Vulnerability of climate change depends on physical, biological and socio-economic characteristics. Low income populations dependent on isolated agricultural systems are particularly vulnerable to hunger and severe hardship. These populations are already barely food-sufficient, even the slightest decline in yields could be very harmful in these areas. The most negative effects are foreseen in dry land areas at lower latitudes and in arid and semi-arid areas, especially for those reliant on rain fed, non-irrigated agriculture (Aydinalp and Cresser, 2008). The rise in temperature cause stress in crops and reduce yields and productivity. Crops that are sensitive to temperature during the growth stages are affected a lot. A shift in growing season is being seen due change in temperature. Irregular and altered patterns of rainfall are severely affecting the crops and water supplies for livestock, which in turn has increased the occurrence of floods and drought, causing soil erosion, disrupting harvesting schedules. Occurrence of new pests and diseases are seen in the places having warmer temperature. Altered temperature has altered the life cycle of pests and intensity of infestations. Rising of sea water level and increased evaporation leads to intrusion of salt water into fresh water making irrigation water more saline harmful to crops. Livestock are sensitive to heat stresses which in turn reduce livestock productivity and increase mortality rates.

Introduction

Climate change may advance more rapidly than anticipated, introducing novel environmental conditions for cultivating horticultural crops. The rise in atmospheric CO2 levels from non-renewable energy sources combustion drives global average temperatures, altering weather patterns worldwide with regional variations (Stocker et al., 2013). Currently, certain regions are already experiencing the effects of extreme weather events such as heat waves or frost, while prolonged droughts pose a growing threat to global food security elsewhere. Climate changes may yield both positive and negative outcomes, but they will undoubtedly alter production conditions and product quality (Kaufmann and Blanke, 2017).

Elevated temperatures can enhance the ability of air to hold water vapor, leading to increased water demand. This process can elevate evapotranspiration rates, potentially depleting soil water reserves and causing water stress in plants during dry periods. Fruit production is particularly vulnerable to water stress, especially in regions where trees lack irrigation. Numerous studies indicate that water stress diminishes crop yields and hastens fruit ripening (Henson, 2008).

Introduction

Climate change is widely acknowledged as the most significant contemporary challenge facing humanity. According to a recent report from the Intergovernmental Panel on Climate Change (IPCC, 2022), the situation has deteriorated further, with 3.3 billion people worldwide highly susceptible to climate change. Current unsustainable development practices are escalating the exposure of ecosystems and populations to climate-related risks. Human activities and their impact on the climate and environment are leading to unprecedented extinctions of animals and plants, resulting in a loss of biodiversity and posing a threat to life on Earth. The diversity of microorganisms is fundamental to maintaining a healthy global ecosystem, as the microbial world serves as the life support system of the biosphere. Although the influence of human activities on microorganisms is less conspicuous and less well understood, a significant concern is that changes in microbial biodiversity and functions will impact the resilience of other organisms, affecting their ability to adapt to climate change. Microorganisms play crucial roles in carbon and nutrient cycling, as well as in the health of animals (including humans), plants, agriculture, and the global food web. Microorganisms inhabit all environments on Earth occupied by larger organisms and are the exclusive life forms in certain environments such as the deep subsurface and extreme habitats. Dating back to the origin of life on Earth at least 3.8 billion years ago, microorganisms are likely to persist well beyond any future extinction events. Despite their vital role in regulating climate change, microorganisms are seldom the focal point of climate change studies and are typically overlooked in policy development. The challenge lies in understanding their intricate role in the ecosystem due to their vast diversity and varied responses to environmental changes.

Introduction

Climate change is a deadliest hazard to life on Earth. Global temperature is rising due to greenhouse gas emissions from the usage of fossil fuels, this result in widespread agricultural and fisheries failure, the extinction of hundreds of thousands of species, and whole towns becoming uninhabitable (Lindwall, 2022). Rising global temperatures are severely killing humans and trees, forcing half of all species to move, worsening water-borne and respiratory ailments in people, and jeopardising millions’ food and water security (Isaacs-Thomas, 2022). Addressing these concerns necessitates a worldwide collaboration to minimise greenhouse gas emissions and promote sustainable behaviours. Climate change affects agriculture production, lowers crop nutritional value, and increases the frequency of extreme weather events. These interruptions jeopardise food production, availability, and access, especially in vulnerable countries. Microbes play an important role in soil health, nitrogen cycling, and ecosystem stability. They impact a variety of soil activities, such as organic matter breakdown, nutrient mobilisation, and plant growth stimulation. However, climate change poses a substantial danger to microbial communities, possibly changing their activities and altering ecosystem dynamics (Wang et al., 2022). Transitioning to a low-carbon economy requires a global effort. Mitigation strategies include enhancing energy efficiency, adopting renewable energy sources, electrifying industrial processes, implementing efficient transportation systems, and introducing carbon taxes or emissions markets.