eChapters

4.1. Water Use Efficiency (WUE)

An efficient irrigation system implies effective transfer of water from the source to the field with minimum possible loss.

To identify the nature of water loss and to decide the type of improvements in the system.

Evaluation of performance in terms of efficiency is prerequisite for proper use of irrigation water.

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate. This chapter, “Moisture in the Atmosphere,” will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth’s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena (Fig. 4.1). We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earthatmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate.This chapter, „Water Vapor in the Atmosphere,“ will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth‘s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena. We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earth-atmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment.
8.1. Expressions Used for Water Vapor in the Atmosphere
The concepts of vapor pressure, saturated vapor pressure, vapor pressure deficit, and dew point has been discussed with detailed explanations:
8.1.1. Vapor Pressure (e)
Vapor pressure is the partial pressure exerted by water vapor molecules in the air. It represents the contribution of water vapor to the total atmospheric pressure. Imagine air as a mixture of gases; the vapor pressure is the „pressure“ exerted solely by the water vapor component of that mixture.

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate.This chapter, „Water Vapor in the Atmosphere,“ will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth‘s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena. We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earth-atmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment.
8.1. Expressions Used for Water Vapor in the Atmosphere
The concepts of vapor pressure, saturated vapor pressure, vapor pressure deficit, and dew point has been discussed with detailed explanations:
8.1.1. Vapor Pressure (e)
Vapor pressure is the partial pressure exerted by water vapor molecules in ,the air. It represents the contribution of water vapor to the total atmospheric pressure. Imagine air as a mixture of gases; the vapor pressure is the „pressure“ exerted solely by the water vapor component of that mixture.

Water, of its very nature, as it occurs automatically in the process of cosmic evolution, is fit, with a fitness no less marvelous and varied than that fitness of the organism which has been won by the process of adaptation in the course of organic evolution.

WATER IS ABSOLUTELY ESSENTIAL FOR ALL LIVING ORGANISMS

The evidence:

Most organisms are comprised of at least 70% or more water. Some plants, like a head of lettuce, are made up of nearly 95% water;

When organisms go dormant, they loose most of their water. For example, seeds and buds are typically less than 10% water, as are desiccated rotifers, nematodes and yeast cells;

Earth is the water planet (that’s why astronomers get so excited about finding water in space).

Water is the limiting resource for crop productivity in most agricultural systems.

WATER IS VERY SPECIAL IN BIOLOGY

Most abundant chemical of life

Special properties:

Abstract

The livelihood security of hill people is closely associated with hydrology of the region. The Himalayas possesses one of the largest reserve resources of freshwater in the form of snow and ice, thereby supporting livelihoods of millions of people. The physiographic constraints of the region restrict irrigation development with the result that, majority of cultivated area remains rainfed. Climate change is also a serious issue concerning hill economy. Its impact on livelihood security is dictated, among other things, through change in hydrology. In addition to highlighting hydrological issues, suggestions are offered on how to deal with water related issues to livelihood enlargement and protection.

Introduction
Waterlogging refers to the accumulation of excessive water in the root zone, leading to anaerobic conditions. This surplus water hampers the exchange of gases with the atmosphere, and biological processes deplete the oxygen supply in both soil and water, resulting in anaerobiosis, anoxia, or oxygen deficiency. In India, approximately 11.6 million hectares, constituting 8.3% of its net sown area, are affected by waterlogging (Planning Commission, 2011). According to Brundtland and Khalid (1987), available estimates indicate an annual global loss of 1.5 million hectares of irrigated land due to salinity and waterlogging. Regrettably, data regarding the occurrence and extent of these issues are inconsistent and incomplete. More recent estimates, provided by Datta and Joshi (1992), range from 5.5 million to 13 million hectares. After conducting a comprehensive global survey, it has been determined that submerged and waterlogged soils cover approximately 5 to 7% of the Earth’s land surface. The total area of waterlogged soil worldwide is estimated to be around 700 to 1000 million hectares. Tropical swamps, rice fields, and floodplains collectively represent nearly 14%, 12%, and 10% of the total waterlogged area, respectively. In India, Odisha, West Bengal, Bihar, and Uttar Pradesh have the highest concentration of waterlogged soil, with an estimated total area of one million hectares. The eastern region bears a significant portion of this burden, with over 20% of the affected land suffering from surface waterlogging, which severely diminishes productivity. Waterlogging is characterized by the soil becoming unproductive and infertile due to excess moisture, creating anaerobic conditions known as waterlogged soils. Waterlogged soil presents a significant challenge to agricultural productivity and soil health, characterized by excessive water saturation that restricts oxygen availability to plant roots. In this chapter, we delve into the multifaceted aspects of waterlogged soil, exploring its causes, defining characteristics, and far-reaching consequences. The serves as a comprehensive overview, underscoring the detrimental impact of waterlogging on agriculture, ecosystems, and human well-being. It identifies key factors contributing to

13.1 Introduction

In agricultural lands, when the pores of the soil within the root zone of the crop get saturated with the subsoil water due to infiltration of high rainfall, excess irrigation or heavy seepage loss in the unlined canal systems, the air circulation within the soil pores get totally stopped. This phenomenon is called as waterlogging. In canal commands where there is continuous flow of water in the canals and canals are mostly unlined, there is heavy loss of seepage which raises the ground water table. This raising water table sometimes comes up to the ground surface which impedes surface drainage. By capillary action, under ground water rises to the crop root zone and submerges the roots of the crops for most of the time. This situation is called as waterlogging which creates salinisation and alkalinisation problems affecting the plant growth.

The height to which soil water rises above the water table by capillary action is called as capillary fringe. Generally, the height of the capillary fringe varies from 1 to 1.5 m. When the water table comes to 1.5 m below the surface of the soil, the land is said to be waterlogged. At times, due to poor drainage conditions, surface water cannot be freely drained out. The stagnate water in these low lying areas also causes waterlogging which enhances the weed growth consequently affecting the crop yield.

3.1. INTRODUCTION 

Transitory waterlogging occurs extensively in both irrigated and dry land agriculture on clay flats and duplex soils. Most of the humid tropical lowlands, with adequate, rain-fed but poor drainage, have the problems of waterlogging, which is further intensified by low water table and poor root aeration. In submerged condition, only root is exposed to excess water and the injury to the shoot is not a primary effect.

The term ‘waterlogging’ is defined as a condition of the soil where excess water inhibits gas exchange of roots with the atmosphere. Waterlogging is different from ‘flooding’ because the latter results in addition factors of partial or complete submergence of the shoot. The waterlogging replaces a gaseous air by liquid water, leading to the gas stresses. Schematic representation of adverse effects of waterlogging on plant growth and survival has been given in Fig. 3.1.

Watermelon (Citrullus lanatus (Thunb.) Matsam. & Nakai, 2n = 2x = 22, family Cucurbitaceae, cross-pollinated crop) is grown commercially in areas with long frost-free warm periods. Three-fourths of the world production is grown in Asia, with China the leading country in production. Watermelon is a nutrient-rich food full of vitamins, minerals and antioxidants. It also contains niacin, thiamin, vitamin B-6, zinc, magnesium and many more nutrients. There are many health benefits to watermelon as it is low in calories so it promotes phyto-nutrients and anti-oxidants essential for the optimization of health.

At global level, China tops in watermelon production (79 million tons) with other countries falling far behind, namely, Turkey (3.9 million tons), Iran (3.8 million tons), and India (2.5 million tons). During 2017-18, India produced 2.5 million tons of watermelon from 0.1 million ha (1 lakh ha) acreage and thus Indian watermelon productivity is 25 tons/ha. Top five states having area more than 10,000 ha in India are West Bengal (17,000 ha), UP (14,000 ha), Odisha (12,000 ha), AP (11,000 ha) and Karnataka (10,000 ha).

Watermelon (Citrullus lanatus (Thunb.) Matsum and Nakai) is an important cucurbit crop throughout the tropical and subtropical regions of the globe. It is an annual creeping vine and native to the Southern part of Africa, most probably the areas around the Kalahari Desert. Presently, more than 1200 cultivars have been developed and are being grown in nearly 122 countries with tropical and subtropical climates. Watermelon is mainly valued for its ripe ‘pepo’ fruits which are consumed as fresh-cut dessert or as juice. The fruits are a rich source of carotenoids, minerals, phenolic compounds, flavonoids, vitamin C and Citrulline, a non-essential amino acid. The red colour of the watermelon flesh is due to the presence of lycopene, the content of which is 40% more than that of tomato. Besides, there is good variation available for f lesh colour ranging from red, pink, yellow, orange, white and green. Owing to the ability to prevent several chronic diseases due to the presence of pigments like lycopene, anthocyanin, carotene, xanthophyll etc., presently watermelon is also considered as a functional food. The exocarp (rind) is also consumed as stewed, pickled or stir-fried or may be used for the preparation of ‘tooty fruity’. Watermelon seeds are considered a good omen and are gifted during Chinese New Year in East Asia. The seeds are also used in the baking and confectionary industries as these contain a characteristic nutty flavour. The seeds are also rich in protein, vitamins as well as omega-3 and omega-6 fatty acids.

Watermelon, Citrullus lanatus under the family Cucurbitaceae (Chromosome number: 2n = 2× = 22) is an important and popular summer season crop of the USA, Middle east, Japan, Africa and India. Watermelon is primarily consumed fresh for their sweet, juicy and slightly grainy flesh and are often eaten as desserts. Watermelon is actually a nutrient dense food. It provides high levels of vitamins, minerals, andantioxidants particularly lycopene and relatively low in calories.
Origin, domestication and adaptation in India
The origin of watermelon was in tropical Africa perhaps in Kalahari Desert, now in Botswana. The progenitor species, Citrullus colocynthis is endemic to Africa. Wide variation of this progenitor species is also found in Rajasthan and Gujarat in India. Wild watermelon seeds have been found in Uan Muhuggiag, a prehistoric site in Libya that dates to approximately 3500 BC. Watermelon was domesticated in Africa and later it was introduced in India. From India it spread to Near East and Asia. The watermelon which was domesticated in Egypt by 2000 BC were not the sweet modern variety. The fruit flesh of wild watermelons is watery, but typically hard-textured, pale-coloured and bland or bitter. The familiar sweet dessert watermelons, C. lanatus, featuring non-bitter, tender, well-coloured flesh have a narrow genetic base, suggesting that they originated from a series of selection events in a single ancestral population.

Now-a-days, a watershed management or watershed development has been fully recognized as a unit for over all development of rainfed areas (Gupta, 2006a and b). Hydrological problems such as excessive runoff, large scale soil erosion, inadequate or faulty drainage and occurrence of droughts are the most significant problems in almost all the rainfed areas. These problems, however, can be alleviated through running watershed based development programmes that recognize the natural topography and water movement patterns of the land.

1.1. Watershed development

Refers to the conservation, regeneration and judicious utilization of all the resources viz., land, water, vegetation, animal and human within a particular watershed in integrated manner.

Water drainage area on earth’s surface from which runoff, due to precipitation, flows into a single to a larger stream, a river, a lake or the ocean.

1.2. Concept of watershed management

Planning and design of soil and water conservation structures such as bunds, waterways, overflow structures, water harvesting structure.

A watershed is an area that provides pathway to the surface or sub surface water flow to a given drainage system. The watershed is a hydrological unit. The area of watershed may vary from few hectares to thousands of square kilometres. The watershed development involves effective management of land and vegetation in order to conserve and improve the quantity of water. The watershed development is a comprehensive and sustainable solution to water conservation (Fig.13.1).
The watershed development has several advantages. It helps in
• Conservation, upgradation and utilization of natural resources particularly land, water and vegetation
• Minimise the inequalities between rainfed and irrigated areas
• Promoting cost effective adoptable simple technologies
• Supply water for domestic ,agricultural and industrial use
• Poverty alleviation and employment generation
• Reducing chemical pollution
• Adopting flood control measures by constructing water storage or impounding structures

Agriculture is world’s single largest employer and probably the most weather dependent of all human activities.  Climate and its variability have been and continue to be, the principal source of fluctuations in global food production. Throughout history, extreames of heat and cold, droughts and floods, and various form of violent weather have wretched havoc on the global agricultural production. With the unprecedented increase in population over past few decades, clearly the mankind faces undertaking task to ensure food and nutritional security for all, considering reduced per capita land, reduced availability of water, depleting biodiversity and need to preserve ecology and environment. In India, of the total geographical area of 328 m ha, about 175 m ha (53 % of total) are categorized as degraded land, of which 150 m ha are subjected to serious water and wind erosion (Singh et al. 1981). Crops are sown in about 180 m ha annually. Since it seems very much impossible to bring more area under cultivation we need to achieve greater efficiency in the natural resources use while conserving the environment by placing greater emphasis on understanding and exploiting climatic resources for the benefits of agriculture.

Technical Term                            Definition

Geomorphological Analysis       Geomorphological analysis is the systematic description of watershedís geometry and its stream channel system to measure

                                                   the liner aspects of drainage network, aerial aspects of drainage basin and relief aspects of channel network.

Watershed

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, scientist geographer, put it best when he said that a watershed is: “that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.”

Watershed is defined as a hydro-geological unit of area from which the rainwater drains through a single outlet. Watershed development refers to the conservation, regeneration and judicious use of all the natural resources (like land, water, plants, animals) by human beings. Watershed Management brings about the best possible balance between natural resources on the one side and human beings on the other. Human beings and the ecology are interdependent. The changes in the environment directly affect the lives of the people depending on it. A degraded environment means a degraded quality of life of the people. This degradation can be tackled effectively through the holistic development of the watershed. A watershed provides a natural geo-hydrological unit for planning any developmental initiative. The approach would be treatment from “ridge to valley”.

A watershed, also called a drainage basin or catchment area, is defined as an area in which all water flowing into it goes to a common outlet. People and livestock are the integral part of watershed and their activities affect the productive status of watersheds and vice versa. From the hydrological point of view, the different phases of hydrological cycle in a watershed are dependent on the various natural features and human activities. Watershed is not simply the hydrological unit but also socio-political-ecological entity which plays crucial role in determining food, social, and economical security and provides life support services to rural people.

Management of watershed in India

It involves management of water, land, energy and greenery, integrating all the relevant scientific approaches appropriate to socio-economic background for a pragmatic development of a watershed. In practice, it means allowing load free rainfall run off from the watershed. Clear outflow imply management of effective soil and water conservation and generating a lush green carpet in whole of the area. In other worlds, it is greening of a watershed through proper management of land, water and energy sources. The comprehensive development of watershed seems to make productive use of all its natural resources and also protect them is termed as watershed management.

The Banave terraces in Indonesia and those in Nepal, Mediterranean are examples of integration of human elements into a system of land management, which is an early achievement in watershed management. Watershed management is not merely anti-erosional and anti-run off approach but also a comprehensive integrated approach of land and water resources management. The approach is preventive, progressive, corrective as well as curative. Here wasted land resources could be fruit fully harvested into a productive face for rural development.