eBook Chapters

Aquaculture is the cultivation of fish, molluscs, crustaceans (shell fish) and aquatic plants in controlled conditions, provides an increasingly significant proportion of food production globally. The sector has represented the greatest growth of all food production systems in the last two decades and an estimated 10% yearly increase in output is likely to bring productivity to a predicted 47 million tonnes in the year 2010 (Pedini and Shehadeh, 1997). Significantly, the greatest contribution to total production and the greatest rate of uptake of aquaculture activity is in the developing world. More than 82% of the total global yield in 1999 was produced by developing countries (GESAMP, 2000) and growth rates between 1984 and 1995 were six times higher than that from developed countries (Rana, 1997; Tacon, 1996).

Learning about water chemistry is often neglected by most of the aquarium owners. By understanding the concepts of water chemistry, they can considerably improve success rate in rearing healthy fishes. It is well known that the quality of water has a direct impact on the health of the fish. But many aquarium owners do not understand the basic internal chemistry of the water, nor do they understand how to correct it or safely adjust it. Until the basics of water chemistry is understood and some common water maintenance techniques are learnt, it will be difficult to maintain a healthy and safe environment for the fish in tank. The water quality is by far the single most important factor for the healthy fish, and the more is known, the better management is expected.

Fish depends for their basic necessities on the water in which they live. The most characteristic feature of an aquarium system is, therefore, the quality of the water available in tanks/aquarium. This water must be obtained from some source, pre-treated to make it suitable for the fish, delivered to the fish in sufficient quantities and maintained in good condition. The water supplied to an aquarium is not pure, but it contains dissolved and particulate materials, some are necessary for up keep of the fish and rests are harmful. Contamination may occur not only at source or from the animals, but often takes place within the aquarium from the materials used for its construction. The number of fish that can be maintained within the aquarium is said to be according to the quality and quantity of the water supplied to an aquarium. However, it is rarely the quantity of water per unit which limits the carrying capacity. The capacity is usually set by the requirement of dissolved oxygen and the accumulation of toxic metabolic products in the aquarium.

2.1 Historical Development

We have seen in Chapter 1 that modeling is about establishing cause effect relationship. Perhaps one of the earliest attempts in this direction is made as early as 1848 in Germany where it was tried to establish a relation between purity and pollution to the occurrence of certain biological organism. But as far as water quality modeling is concerned the first major breakthrough in this direction is the effort of Streetor and Phelps (1925) in oxygen sag curve. They developed model for estimating DO and BOD in Ohio River. The work of O’Conner (1962) for bacteria models are major milestone in pre-computer era modeling.

With the advent of computer during 1960s complicated kinetics and time variable simulation came into being. Most of the workers presented their efforts in terms of linear programming based water management models concerning waste discharge. Thomann(1963) has formulated linear programming based models for dissolved oxygen in an estuary. So a stage is set for study of eutrophication through modeling, but the problem is determination of values of various parameters in these equations.

During 1970s models expanded in terms of complexities mainly because of enhanced computational facilities. Two dimensional and dynamic framework has started replacing one dimensional steady state configurations. In the same year, Di Toro presented an analysis of the steady state two dimensional concentration distribution that results in the horizontal plane from the continuous discharge of a non-conservative substances (DO and BOD) into an infinite body of water.

Water quality standards (Classification)

Some countries have established national standards and criteria for evaluation and classification of water quality. The classification of irrigation waters has been made according to one or more of the following criteria.

1.    Salinity or total concentration of soluble salts (EC)
2.    Sodicity hazards (SAR)
3.    Alkalinity hazards (RSC)
4.    Combined evaluation on the basis of EC and SAR by USSL diagram
5.    Combined evaluation on the basis of EC and Adj. SAR
6.    Combined evaluation on the basis of EC, SAR and RSC

1. Relative Water Content

Relative water content (RWC) is an important parameter to measure the water status of plant tissue. High RWC, under moisture stress, denotes ability of plants to tolerate drought. (Ritchi et al. 1990). RWC and water potential have often been reported as indicators of drought tolerance (Schonfeld et al. 1988).

Leaf water status may be estimated by measuring the RWC following Barrs and Weatherlay’s (1962) method as given below:

5.1 Introduction

A reservoir that collects and harvests in-situ rainfall as well as runoff from the catchment area can be used for many purposes: the most important of which is the supply of water to crops as supplemental irrigation. The water of the reservoir can be used for domestic and industrial uses. It is also a good source for recreational use. Total water demand of the reservoir including irrigation to different crops in different seasons, domestic and other non agricultural uses are to be assessed. While estimating the crop water requirement and irrigation requirement, various crops to be grown in the service area of the reservoir, their water requirements, crop duration, extent of coverage and water management practices followed are to be taken into consideration. Multiplying the irrigation requirement with crop coverage area, volumetric irrigation water requirement of crop can be found out. Summation of irrigation requirement of all crops grown in service area of the reservoir gives total irrigation demand of the reservoir.

Small farm reservoirs are normally used for irrigation to crops as well as to meet the live stock water demand. Normally the large live stocks like horse, cattle require 20 thousand litres of water per head per year whereas the small live stocks like sheep, goat, pigs require 2 thousand litres of water per head per year. Adding the irrigation demand to the livestock demand, total water requirement of the reservoir is calculated. In addition to this, water used for industrial, domestic and other sectoral purposes are to be added to irrigation and livestock demand to estimate the total water demand of the reservoir.

4.1 Introduction

A reservoir that collects and harvests in-situ rainfall as well as runoff from the catchment area can be used for many purposes: the most important of which is the supply of water to crops as supplemental irrigation. The water of the reservoir can be used for domestic and industrial uses. It is also a good source for recreational use. Total water demand of the reservoir including irrigation to different crops in different seasons, domestic and other non-agricultural uses are to be assessed. While estimating the crop water requirement and irrigation requirement, various crops to be grown in the service area of the reservoir, their water requirements, crop duration, extent of coverage and water management practices followed are to be taken into consideration. Multiplying the irrigation requirement with crop coverage area, volumetric irrigation water requirement of crop can be found out. Summation of irrigation requirement of all crops grown in service area of the reservoir gives total irrigation demand of the reservoir.

4.2 Water and Irrigation Demand of Crops

Of the various demand of water from the reservoir, irrigation demand of crops grown in the command area of the reservoir is very important. Most of the crop water demand is met from rainfall. However, when the rainfall is deficient to meet the crop water demand, then the deficit is met from the stored water of the reservoir in the form of irrigation, more commonly called as supplemental irrigation. The irrigation to the crops is required mostly to meet the evapotranspiration requirement of the crop. Before discussing the water and irrigation demand/requirement of crops, it is essential to know some commonly used terms frequently used.

Introduction

The eastern states of India comprising of Bihar, West Bengal, Odisha, Chhattisgarh, Jharkhand, Assam and eastern Uttar Pradesh occupy about 21.85% geographical area and supports 34% human and 31% livestock population of the country. Agriculture is the mainstay of economy in these states, since 83% population living in rural areas depends on it for their sustenance. The region has about 2.73 M ha of total area under reservoirs, ponds, tanks, lakes, brackish water, etc. besides 15046 km length of rivers and canals constituting about 18 percent of country’s utilizable water resources. The average rainfall in eastern region varies from 1091 to 2477 mm with a regional average of 1526 mm, which is sufficient and substantial for growing a variety of crops. However, the irrigated area in the region is 39% as against 45%, the national average.

1.1. Status of irrigation in Tamil Nadu

Geographical area of 13 million hectares is ranked eleventh in size among the Indian states.

Net area sown is about 6 million hectares.

3 million hectares or 50% get irrigation facilities.

Introduction
Given increasing demands, dwindling resources, and climate-induced uncertainties, water resource management is a critical challenge in the 21st century. Integrating Information Technology (IT) into water resource management offers transformative solutions to optimize water usage, monitor resources, predictshortages, and enhance distribution efficiency. IT tools such as remote sensing, geographic information systems (GIS), artificial intelligence (AI), Internet of Things (IoT), and big data analytics are at the forefront of this evolution, enabling more effective planning, decision-making, and resource sustainability.

1.1 Introduction

Climate change is evident from the observation of increase in global average air and ocean temperatures, precipitation and extreme rainfall, widespread melting of ice, storms / storm surges flooding and rising global mean sea level, as recorded in the Fourth Assessment Report of IPCC. Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850). 

10. 1 Land and Water Resource

India has got the world’s 2. 45% area and 16. 87% of population with only the 4% of available fresh water (Table 10. 1). This indicates the necessity of development of water resources and optimal use of it. India at macro level does not have short of water. But the shortage of water is due if not properly managed by conservation and sector wise utilization.

10.1 Land and Water Resource

India has got the world’s 2.45% area and 16.87% of population with only the 4% of available fresh water (Table 11.1). This indicates the necessity of development of water resources and optimal use of it. India at macro level does not have short of water. But the shortage of water is due if not properly managed by conservation and sector wise utilization.

The water resource potential of the country has been assessed by different agencies in different time (Table 11.1). It is observed that the latest estimate of 1869bcm (1993) are within the little variation of the estimates since 1954. The utilizable water resources of the country are assessed 1123bcm by CWC (1993) of which 690bcm from surface water and 433bcm from ground water sources. This 690bcm can be harnessed if matching storage structures are built. The surface water utilizable potential may increase by 220bcm if inter-basin transfer

Water Resources: Classifications of water: Groundwater, surface water and Virtual Water; Conjunctive use of water in agriculture; Water resources in different states and Stakeholders of water use.
Introduction
Despite fact that more than two-third of the earth’s surface is covered with water, currently, near about 450 million people in 29 countries are facing severe water shortage and at least 20 percent more water would be required to feed additional 3 billion populations by 2025. About 97.5 percent of ocean-sea water is not available due to its salinity and 2.49 percent is locked up in ice and only 0.01 percent is technologically available and economically accessible water either from surface or ground water sources for human uses. So water saving technologies developed so far is very pertinent to propagate amongst the users. Water is an essential natural resource for sustaining the environment and supporting life where the agriculture is the major user of water resource. Water is an indispensable for sustainable agricultural growth and development. Previously, rainfed agriculture was associated primarily with conservational land treatments to check soil erosion and land degradation.But in the areas of medium to heavy rainfall, there is ample scope of tapping excess rain water through suitable water harvesting structures constructed for this purpose for its subsequent uses as irrigation or to apply lifesaving irrigation to the crops which should also come under the purview of water management for crop production. Although there is a difference in the objectives of water management where there is abundant availability of water from continuous flow connected with perennial sources or lakes and rivers and that of from restricted or limited supply from collection of excess rain through water harvesting structures.The former is associated with to obtain as much as yield of crop per unit area under water application and later is associated with increasing productivityof crop per unit of water application even under rainwater recycling and its effective management for the purpose of irrigation. Hence, both the rainwater and irrigation water are considered to be equally important to context of

Land and water resources are central to agriculture and rural development, and are intrinsically linked to global challenges of food insecurity, land degradation , poverty, climate change adaptation and mitigation that affect the livelihoods of millions of rural people across the world. Current projections indicate that world population will increase from present figure of 6.9 billion to 9.1 billion in 2050. As a result, the world food demand will increase. Since, both land and water resources, the basis of our food production, are finite and already under heavy stress, so future agricultural production will need to be more productive and more sustainable at the same time. The largest contribution to increases in agricultural output will most likely come from intensification of production on existing agricultural land. This will require widespread adoption of sustainable land management practices, and more efficient use of irrigation water through enhanced flexibility, reliability and timing of irrigation water delivery. The prevailing patterns of agricultural production needs to be critically reviewed.

1. Introduction to Water Resources in Agriculture

Water, the quintessential life force for agriculture, intricately intertwines its significance throughout the fabric of global farming practices.

1.1 Significance of Water in Agricultural Practices

1.1.1 Sustenance of Plant Life

• Beyond its role as a life sustainer, water emerges as the very essence that propels plant development. It acts as the vital catalyst for photosynthesis, the engine of plant growth. This intricate process is the heart of the plant’s ability to convert sunlight into energy, driving robust development from seed germination to harvest.

Introduction

Water is a precious natural resource vital, for sustaining all life on the earth. It is in a continuous circulatory movement - hydrologic cycle. It is not uniformly distributed in time and space. Due to its multiple benefits and the problems created by its excesses, shortages and quality deterioration, water as a resource requires special attention. On a global scale, total quantity of water available is about 1600 million cubic km. The hydrological cycle moves enormous quantities of water about the globe. However, much of the world’s water has little potential for human use because 97.5% of all water on earth is saline water. Out of remaining 2.5% fresh water, most of which lies deep and frozen in Antarctica and Greenland, only about 0.26% flows in rivers, lakes and in the soils and shallow aquifers which can be readily used. Sustainable water management in India is fast becoming a necessity, with the looming crisis over water resources in the country threatening the security and livelihood of the population and the environment over the coming decades. Managing water resources, river catchments, and coastal zones are outstanding challenges of today and tomorrow’s. Global changes ask for a comprehensive scientific approach, an international multi-disciplinary orientation and require a new mind-set towards water and coastal management problems.

2.1. Introduction

Water plays a pivotal role in this earth system. The withdrawal of water for irrigation is about 70% of the global freshwater. Water use efficiency is less than 50% in many countries. It has been forecasted by the Food and Agricultural Organization (FAO, 2015) that global water requirements will be increased by 50% by the year 2050 to meet the demands of agricultural water use. This is so because food demand will be higher for the growing human population. We have entered into an earth system where everything living has evolved and developed (Cosgrove and Loucks, 2015). There has been a new geological scenario, some say Anthropocene (Crutzen, 2002; Williams et al., 2011). Consequently, freshwater will increasingly be a scarce and the costliest resource in the future, which needs to be managed properly.

Surface Water Resources

Surface water is a general term describing any water body which is found flowing or standing on the surface, such as streams, rivers, ponds, lakes and reservoirs. Surface water originates from various combinations of sources:

1. Direct precipitation - rainfall which falls directly in the surface water body;
2. Surface runoff - rainfall which has fallen onto the surrounding land and that flows directly over the surface into the water body;
3. Interflow - excess soil moisture which is constantly draining into water body; and
4. Water table discharge - where there is an aquifer below the water body and the water table is high enough, the water will discharge directly from the aquifer into the water body.

The quality and quantity of surface water depends on a combination of climate and geological factors. The recent pattern of rainfall, for example, is important in enclosed water bodies such as lakes and reservoirs where water is collected over a long period and stored. The water storage in streams and rivers is in a constant stage of movement and depend on the weather conditions.

4.1 Introduction

India is a land of many rivers, lakes, ponds, coastal, marines and mountains. Its geographical area of about 329 million hectare is crises crossed by a large number of small and medium, large rivers, some of them figuring amongst the mighty rivers of the world. The rivers and mountains have a greater significance in the history of Indian civilizations, development, religious and spiritual life. It may not be an exaggeration to say that the rivers are the heart and soul of the Indian civilizations

India is a union of States with a federal set up. Politically, the country is divided into 26 States and 7 Union Territories. A major part of India’s population of 869 millions (1991 census) is rural and agriculturally oriented for whom the rivers are the source of their life. India is a land of many religions, diversity of cultures and languages. The different regions of the country have different cultural, linguistic and other ethnic groups. The land and people present a vast panorama of diversity in unity. Physiographically, India may be divided into seven well-defined regions.

4.1 Soil Moisture Tension

Soil moisture tension is a measure of the tenacity with which water is retained in the soil and shows the force per unit area that must be exerted to remove water from soil. The tenacity is measured in terms of the potential energy of water in the soil measured, usually with respect to free water. It is usually expressed in atmospheres, the average air pressure at sea level. Other pressure units like cm of water or cm or mm of mercury are also often used (1 atmosphere = 1036 cm of water or 76.39 cm of mercury). It is also sometimes expressed in bars (1 bar = 106 dynes / cm² = 1023 cm of water column. 1 millibar = 1/1000- bar).

Soil moisture tension is brought about at the smaller dimensions by surface tension (capillarity) and at the higher dimensions by adhesion. Buckingham (1907) introduced the concept of ‘capillary potential’ to define the energy with which water is held by soil. This term, however, does not apply over the entire moisture range. In a wet soil, as long as there is a continuous column of water, it might be called ‘hydrostatic potential’, in the intermediate range the term ‘capillary potential’ is appropriate. In the dry range the term ‘hygroscopic potential’ would be suitable. However, the term ‘soil moisture potential’, ‘soil moisture suction’ and ‘soil moisture tension’ are often used synonymously to cover the entire range of moisture (Khonke, 1968).

Water is an essential component of all living things. Although once believed as a resource with a never-ending supply, it has now been understood that water is becoming increasingly scarce and therefore a proper management is necessary to keep a sustainable food production (Kannan & Anandhi, 2020). A continuous and safe supply of water is indispensable for the food industry where it has numerous applications along the agriculture and food production processes.

Riboflavin or Vitamin B₂
Introduction

Riboflavin (synonymous with lactoflavin, vitamin G and vitamin B2) is a yellow green, fluorescent, water soluble pigment widely distributed in plant and animal cells. The organic formula of riboflavin is (6, 7-dimethyl)-9-(D,1-ribtyl)-iso-alloxazine. The empirical formula is C₁₇H₂₀N₄O₆. Riboflavin is very sensitive to both visible and ultraviolet light. All manipulations with riboflavin or riboflavin containing materials should be carried out in subdued light or in low actinic glassware. Even subdued daylight may be destructive but artificial light of an intensity of 6 candles per squarefeet or less is permissible. Irradiation of alkaline solutions yields lumiflavin (6, 7, 9-trimethylis-alloxazine) and in acid solutions lumich rome (6.7 dimethyl alloxazine) is formed, which is characterised by a blue fluorescence. One of the distinguishing properties of riboflavin is its yellow-green fluorescence in neutral solutions which reaches a maximum at pH 6.7 to 6.8.

Water Requirements

Dairy plant requires large quantities of water on a daily basis for processing and cleaning purposes. Normally the specific water consumption ranges from 1000-5000 litres per 1000 litres of milk processed. The actual requirement can vary between dairies and is a function of 
    a)    Manufacturing process or manufacturing profile.
    b)    Auxiliary processes such as steam generation, design of the refrigeration processes and extent of social services.
    c)    Multiple use/reuse.
Water is a very valuable basic natural resource  and needs careful consumption. The water supply system in a dairy plant should be designed in such a way that consumption for each manufacturing department and auxiliary processes can be determined. This makes it possible to influence water consumption directly, and major losses can be determined very rapidly.

4.1 Introduction

A farm pond is basically small scale water harvesting and water recycling structure. It harvests water mainly in the rainy season when there is abundant rainfall producing sufficient runoff and the harvested water may be used for single or multiple cropping. When there is deficient supply of water to the crops it may supplement as supplemental irrigation. The leftover water in the pond can be used for growing another crop in winter when there is no or less rainfall. Ij addition, the stored water in the pond can be used for domestic and other uses and rearing fish. Thus it serves as viable medium for integrated farming system in rainfed farming ecosystem. Before designing a pond in a given location, it is very important to estimate the total quantity of water supply to the pond. The two main sources of water supply to pond are (i) in situ rainfall and (ii) runoff (some times called as discharge) generated from the catchment and conveyed to the pond. Some times there is groundwater contribution to the pond when the pond is unlined and the underlying groundwater table with reference to the ground level is at lower elevation than the depth of water in the pond such that there is a hydraulic gradient in the direction of underlying groundwater level to the water level in the pond.

The demand for nutrients is rising, along with the population, which is rapidly expanding. The sustainability of life on earth now places a high focus on protecting the sources of sustenance. In this regard, aquaculture has a crucial role to play. The regulated raising of fish and other breeds in a particular environment is known as aquaculture. The natural resources and other elements required for sustainable development can be preserved using this method. The promotion of the value of nutrients and the expansion of employment prospects in the future are both made possible by aquaculture. Biofloc fish farming, which has set trends in fish farming all over India, facilitates recycling and reusing of the nutrients in the culture medium by filtering the unwanted substances and metabolites and converting them into nutrients, which benefits the zero exchange of water.

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.

Watershed is defined as a natural hydrological unit that covers a specific land surface area from which runoff passes through a common outlet or area with common drainage or outlet. In simple terms, it implies a catchments or drainage basin from which water drains towards a single channel. It may extend over a few acres only or may cover thousands of acres.

Watershed management is the integration of technology within the natural boundaries of a drainage area for optimum development of land, water and plant resources to meet the basic minimum needs of the people in a sustained manner.

It is also defined as the development and management of watershed resources in such a manner as to achieve optimum production without deterioration of resources base or disturbing the ecological balance. It is also termed as “Resource centered technology” since it helps in assessment, augmentation and optimal utilization of all natural resources viz., land, water and vegetation, it prevents deterioration of resources and at the same time ensures sustained productivity of land to meet basic needs of people.

ABSTRACT

The major part of the agriculture in India is Rainfed. The increasing pressure of population on land has resulted into over exploitation of land, water and other ecological resources, resulting in water scarcity, land degradation and rapid depletion of ground water-table. Government of India has adopted watershed management strategy to address these problems, but all existing watershed management programmes are mainly fragmented and governed by different departments. This has resulted in formation of providing better service delivery and governance. In this study an attempt is made to identify the scope of convergence between National Rural Employment Guarantee Act (NREGA) with Integrated Watershed Management Programme (IWMP) for generation of social capital and self-employment in the command area of a watershed using geospatial technology.

7.1 Introduction

There are numerous wavelength dependent phenomena that may be used to modulate the wavelength of incident light source. These are wavelength dependent absorption, luminescence, dispersion, interference and scattering. Wavelength modulated sensors use a broadband source, a wavelength modulator or measurand (i.e. analyte), a form of spectrometer (using prisms, gratings or interference filters), a detector (single photodiode or array) and signal processing unit. Silicon photodiode is cheap and can be used for detection but it limits the detection wavelengths to the region 400 to 1050 nm. The sensitivity or the resolution of the wavelength modulated sensor depends on the characteristics of the detector, the inherent resolution of the spectrometer, mechanical stability of the modulation unit and the spectrometer, and the capability of the signal processing unit. However, wavelength modulated sensors do not require any form of referencing like intensity modulated sensors. In intensity modulated sensors, loss in intensity occurs due to connectors and splices, microbending, mechanical creep and misalignment of light sources and detectors due to environmental effect. Further the fluctuations in light source can affect the performance of the sensor. Thus, for intensity modulated sensors one needs referencing to cancel out these losses. In some intensity modulated sensors two wavelengths are used. One wavelength is used to cancel out all of the losses while the second is used to sense the measurand.

Wavelength detection is relatively easy if the spectral changes result from changes in chemical indicator dyes, fluorescence, phosphorescence, or black-body radiation. In these cases the incident and emitted wavelengths are far apart and therefore detection is easy. If the spectral change occurs due to mechanical movement, then the wavelength filtering mechanisms must have sufficient resolvable spectral points. The reasons for using fluorescence in the fiber optic sensors are well known. Fluorescence is intrinsically more sensitive than absorbance and is more flexible in that a great variety of analytes and physical parameters are known to change the emission of particular fluorophores. The fluorescence based sensors utilize the change in the intensity, lifetime or colour of fluorescence as the affected parameter by the measurand. That means, any interpretable observation of fluorescence can be made the basis of a sensor. In this chapter we shall first describe luminescence phenomenon and then various physical and chemical fiber optic sensors based on wavelength modulation and fluorescence phenomenon.