eChapters

6.1. Humus

Fraction of organic matter.

Complex and resistant mixture of brown or dark brown amorphous and colloidal organic substance.

6.2. Humus formation

1. Decomposition: Chemicals in the plant residues are broken down by soil microbes.

Simpler chemicals are metabolized into new compounds in the body tissue of soil microbes.

New compounds are subjected to further modification and synthesis as the microbial tissue is subsequently attacked by other soil microbes.

3.1. Natural cross-pollination

Breeding procedures in any plant species of economic importance are guided by its reproductive system particularly, pollination mechanism. In the cereal crops such as maize, pearl millet etc., where cross-pollination is facilitated by wind, the breeders have developed schemes for commercial exploitation of dominance and epistatic genetic variation through hybrid and population breeding. In contrast in self-pollinated crops, the efforts are always made to exploit additive genetic variation primarily through pedigree and mass selection.
 
In pulses, self-pollination is a rule and pigeonpea is no exception. However under field conditions, occurrence of hybrid plants in the populations is not uncommon; and it happens due to some degree of natural out-crossing that took place in the preceding generation. This type of partial natural out-crossing in pigeonpea is affected by a variety of insects (Fig 10) which forage on its large flowers to collect the nectar. These minor incidences of out-crossing are the primary source of varietal deterioration. Recently, the pigeonpea breeders converted this constraint into an opportunity for genetic enhancement of yield through exploitation of hybrid vigor and developing commercial hybrids.

India has emerged as the second largest producer of vegetables 176.17 mt after China 573.93 mt in the world and is gradually striding towards achieving food and nutritional security at national level. The average productivity of vegetable crops is 17.6 t/ha (NHB, 2015) which is comparatively lower than the productivity of China (23.4t/ha), Spain (39.3t/ha) and USA (32.5t/ha). The lower productivity could be attributed to limited use of quality seeds, inefficient production management, impact of biotic stress and climatic factors during crop production. Among the limiting factors limited availability of quality seed is one of the important factors. Since, the performance of other inputs is also depend on the quality of seed. At present the seed replacement rate among vegetable crops is around 25%, whereas highest in cabbage (>90%) followed by tomato, capsicum, bitter gourd, muskmelon, bottle gourd etc.The use of hybrid seed is in increasing due to higher productivity, tolerance to biotic and a biotic stresses and better market value than the open pollinated varieties but the higher price of the hybrid and their availability is still a constraint in adopting the use of hybrid seeds among small and marginal farmers.

Three types of water movement within the soil are recognized. They are

1. Saturated flow
2. Unsaturated flow
3. Water vapour movement

Saturated flow

This occurs when the soil pores are completely filled with water. This water moves at water potentials larger than 33 kPa. Saturated flow is water flow caused by gravity’s pull. It begins with infiltration, which is water movement into soil when rain or irrigation water is on the soil surface. When the soil profile is wetted, the movement of more water flowing through the wetted soil is termed percolation.

Hydraulic conductivity can be expressed mathematically as

INTRODUCTION
Hydraulics is the study of liquids and their behavior, specifically focusing on the use of pressurized fluid to generate power in engineering systems. Hydraulic systems operate by applying pressure to a small amount of fluid, which in turn generates significant power. The development of hydraulic technology has enabled major advancements, such as lifting heavy loads and rotating large shafts with minimal effort through mechanical linkages.
Compared to mechanical and electrical systems, hydraulic power systems offer greater flexibility and produce more power relative to their size. They also provide quick and precise responses to control inputs. As a result, hydraulic systems are widely used in modern applications such as aircraft, automobiles, heavy industrial machinery, and various machine tools. This article will focus on the hydraulic systems used in tractors.
HYDROSTATIC TRANSMISSION
Hydrostatic transmissions rely entirely on hydraulics, using the power of oil to transmit energy. The system consists of two main components: a variable displacement pump and a hydraulic motor. The pump’s displacement is controlled by a movable swash plate, which adjusts the piston stroke. Essentially, the system operates as a variable-displacement hydraulic pump driving a fixed-displacement hydraulic motor.
The key benefits of hydrostatic transmissions include the ability to infinitely vary ground speed and rapidly change directions. They are also known for their reliability, with self-protecting features that prevent operator abuse.
Additionally, foot pedal-controlled systems have a built-in safety feature that allows for a controlled stop simply by lifting the foot from the pedal. However, hydrostatic transmissions have some drawbacks, including high cost, sensitivity to contamination, and slight power loss at the PTO shaft. Additionally, when

In drip irrigation water is distributed throughout the field from a system of pressurized pipelines. The pressure must be sufficient to overcome the frictional losses and elevation differences. The system also deserves discharge from all the emitters and the emitters must dissipate the pressure difference between the inlet to emitters and atmospheric pressure.

The flow through the drip pipes may be laminar or turbulent or a combination of both. The laminar flow is characterized by the layers of cylindrical tubes of which the maximum velocity is at the center about double of the average velocity. The turbulent flows having pulsatory cross current velocities and maximum velocity is about only 1.25 time of the average velocity. Turbulent f lows loss more energy than laminar flow due to development of the cross current velocity.

Reynolds Number

The criterion for distinguishing the flow from laminar to turbulent was developed by Osborne Reynolds (1842-1900) and was named as Reynolds number; Re . The Reynolds number in circular pipes flowing full is expressed as

14.1 Introduction

Hydro-electric power is electricity produced by the movement of fresh water from rivers and lakes. Gravity causes water to flow downwards and this downward motion of water contains kinetic energy, that can be converted into mechanical energy, and then from mechanical energy into electrical energy in hydro-electric power stations. (“Hydro” comes from the Greek word hydra, meaning water). At a good site hydro-electricity can generate very cost-effective electricity.

Abstract

The Mesozoic sediments contribute around 54% of the oil and 44% of the gas reserves of the world (Bois et al. 1982). Indian Mesozoic basins occupy an area of about 400 x 103 sq. km and are characterized as frontier basins under category II - IV. These basins are mostly overlain by the Deccan Traps of Late Cretaceous age and are least explored. Deccan Syneclise is one of the largest Mesozoic basins in India, covering an area of ~ 273 x 103 sq. km. Geophysical studies have inferred hidden sub-trappean Mesozoic sediments with thickness up to 2.5 km. It is considered that requisite heat generation due to Deccan Trap volcanism soon after the Cretaceous sedimentation may have acted as a catalyst in hydrocarbon generation. Surface geochemical prospecting surveys along with carbon isotopic studies have been used to assess hydrocarbon generation potential of this part of the basin. The area adjoining Nandurbar beneath Narmada-Tapti region of Deccan Syneclise was selected for geochemical studies where geophysical studies have shown considerable sediment thickness. Surface geochemical studies indicate the generation of light gaseous hydrocarbons, C1 and SC2+ in the range of 3 to 1187 ppb and 1 to 1449 ppb, respectively. The carbon isotopic signatures of selected soil gas samples dC13 CH4 in the range of - 24 to -39.4‰ PDB) suggest thermogenic origin

Abstract

A total of 30 groundwater samples were collected in four different seasons (Pre Monsoon, South West Monsoon, North East Monsoon and Post Monsoon) from the coastal aquifers of Kalpakkam region of Tamilnadu. The samples were collected covering the seasonal and lithological variations to infer the influence of natural geochemical processes and anthropogenic sources on the groundwater chemistry. The collected samples were analysed for the parameters like EC, pH and Major ions. The saturation index of silicates and carbonates shows that state of saturation to over saturation, but the sulphate minerals is dominantly under saturated. In the inverse modeling three models are obtained using PHREEQC and the error percentage is noted as 7.45%.

Abstract

In Gadilam river basin, groundwater is found in both hard rock and sedimentary terrain and is the most important source of rural/urban drinking water supply. Gadilam river basin has gained its importance due to the presence of Neyveli Lignite open cast mine (NLC), group of industrial estate (SIPCOT), extensive depressurization of Cuddalore aquifer and boreholes of New Veeranam Scheme (NVS) in the downstream of the basin. A total of 178 water samples were collected in four different seasons at various lithologies. The collected samples were analyzed for various physico-chemical parameters using standard procedures. Geochemical indicators of groundwater were used to identify the chemical processes that control hydrogeochemsitry. Interpretation of hydrogeochemical data suggests that leaching of ions followed by weathering and anthropogenic impact controls the chemistry of the groundwater. Isotopic study reveals that recharge from meteoric source in sedimentary terrain and rock water interaction with significant evaporation prevails in hard rock region. This thorough understanding helps us to make judicial usage and to maintain the quality of this commodity.

Abstract

Quality of water is affected by natural and man induced contamination to groundwater system. Area chosen for study has gained its own importance due to the location of two lignite mines and a Thermal power plant in operation. Extensive large scale pumping of water is done for lignite mining. The mine drainage and drainage from thermal power plant along with agricultural return flow from lignite charged waters increases the severity of problem. In order to achieve a panacea for the above-mentioned situation, the study has incorporated and integrated in all related factors to get a meaningful interpretation for groundwater quality and quantity management in and around Neyveli area. The frequent failure of monsoon has added to the existing problem of over exploitation. To attain a panacea for water chemistry groundwater samples were collected for four different seasons. Higher EC and TDS values are observed in Southeast and Southwest part of the study area. In Southwest monsoon and Summer seasons HCO₃Cl dominates the anions, with few representations for SO₄. In Northeast monsoon and Post monsoon season Na + K – Ca + Mg is the dominant. Thermodynamic, studies reveal that groundwater of the region are stable with Kaolinite stability field in all the silicate systems. Bicarbonates derived from silicate mineral weathering are noted in the NW, Northern and in the mining region. These regions are located in the NW and NE part of the study area. Comparison of water quality to standards shows that the water can be used for drinking and for irrigation purposes except in few locations.

Introduction

Water is among the most precious gifts of nature to mankind. Most of the ancient towns of the world grew on the banks of the river, and some of the ancient civilizations are known by the names of rivers. Rivers have always been important sources of drinking water and the means of sustaining human, animal and plant life. Whenever one is dealing with water resources development and utilization, it has to be kept in mind that not only quantity of water but also quality of water is very important. The well being and development of our society is dependent on the availability of water. An increase in groundwater development and utilization for industries and urban water supply has created improper disposal of liquid waste. Defective well constructions, sewage and waste disposal in man made lakes with in the city, open quarries with water and failure to seal the abandoned wells in city area have provided possible openings for downward movement of polluted water into subsurface formations without undergoing the process of natural filtration.

6.1 Introduction

When rainfall strikes a ground surface, some losses like initial and infiltration will occur. After these losses are fulfilled, runoff will begin. The runoff will ultimately reach a stream. The main routes through which runoff flows are (i) overland flow, (ii) interflow and (iii) groundwater flow. Overland flow which is also called as surface flow flows over the land mass and reaches a stream. Overland flow soon reaches a stream and if it occurs in sufficient quantity, it forms an important element in the formation of flood peaks. In small and moderate storms, there may have predominant initial and infiltration losses resulting minimum amount of surface runoff and this is especially true in case of permeable soils. If the soil is impermeable, then there may have reasonable runoff. However, surface runoff is an important factor in streamflow only for heavy or high intensity rainfall.

Water is a social requirement. Society now become aware about it’s dependence upon water and hence realized the importance of water in sustaining not only the development but also life. Water: too little, too much, too dirty; is general scenario in the world. But with increase in population water become limiting resource and is becoming scarcer and scarcer day by day. As water become scarcer commodity, the users (stakeholders) become more conscious regarding their share in water and ultimately this situation may lead to water conflicts. Earlier water related problems were generally tackled by hydro-engineers, but now in present climate changed scenario these problems go beyond the hydraulics and hydrology. Now a days politicians, ecologists, Non Government Organizations (NGOs), the media and the stakeholders etc are playing a crucial role in decision making in respect to water management issues. Now water projects are designed in reference to social context (Social context means cultural, economic, political, sociological, legal and other such aspects). When social factors are taken into consideration while tackling the water problems, it could not possible to satisfy all involved. Thus it is required to agree upon a compromise solution acceptable to all. Over recent few decades, information and communication technology (ICT) flourishes with great advances. It provides the ways to search for compromise solutions. In this chapter information, hydroinformatics, evolution of hydroinformatics and role of internet in hydroinformatics are discussed.

In this era of computer, mathematical models become integral part of hydrologic studies due to advancement in soft technology. But question always arises as ‘Why should modeling?’ It was well expressed by Rosenblueth and Wiener (1945) as

No substantial part of the universe is so simple that it can be grasped and controlled without abstraction. Abstraction consists in replacing the parts of the universe under consideration by a model of similar but simpler structure. Models, formal or intellectual on the one hand, or material on the other are thus a central necessity of scientific procedure.

Hydrological cycle involves four major steps, Viz., Evaporation, Transpiration, Condensation and Precipitation. Though the cycle has neither a beginning nor an end, the concept of cycle begins with the water of oceans, since it occur nearly ¾ of the Earth’s surface. Radiation from the Sun, evaporates water as water vapour from the oceans into the atmosphere. The water vapour rises and collects to form clouds. Under certain condition, the cloud moisture condenses and falls back to the Earth as rain, snow, hail etc. Precipitation reaching the Earth surface may be intercepted by vegetation or enter into the soil, may flow as run-off or may evaporate.

Evaporation may be from the surface of the ground or from free water surface. Transpiration may be from plants.

Condensation: The physical process by which a vapour becomes a liquid or solid – opposite of evaporation.

Water is the most important natural resource that governs and exercises control on living organisms on earth besides supporting all human activities. The demand for water is almost increasing at exponential rate due to increase in population and industrialization. All sectors of agriculture including crop production, horticulture, animal husbandry, poultry and fi sheries primarily depend upon water. Water scarcity can cause all kinds of miseries. The water exists in all 3 different forms on earth. It exists as snow or ice in glaciers and ice caps, liquid water in rivers, lakes, streams, tanks, ponds and as groundwater storage. The water exists in all three different forms in the atmosphere. The clouds may contain fi ne ice particles, tiny water droplets and as well as water vapour. The air in atmosphere also contains water vapour. It is estimated that 97% of water is salt water and remaining 3% of water is pure and fresh water. Approximately two-thirds of the fresh water is trapped in glaciers and ice caps. Most of the fresh water (30%) exists as groundwater. About 0.7% of fresh water exists as soil water and 0.3% a fresh water accounts for surface water resources and water present in the atmosphere as water vapour, water drops and ice particles. The circulation of water between oceans, earth and atmosphere forms hydrologic cycle.
2.1. Hydrological Cycle
The hydrological cycle explains the continuous recirculation and transport of water between the atmosphere, oceans and earth. It is a very complex system that has many sub cycles associated with it. For example, the water from earth surface, oceans and water bodies get evaporated due to heat energy received from the sun in the form of incident solar radiation (Fig.2.1).

Water is fundamental to life, supporting ecosystems, driving economies, and sustaining human well-being. However, the availability of this essential resource is increasingly threatened by hydrological drought, a complex phenomenon characterized by prolonged deficits in surface and subsurface water supplies. Unlike meteorological drought, which is defined by precipitation shortages, hydrological drought manifests as reduced stream flow, diminished lake and reservoir levels, and depleted groundwater, impacting water availability long after the rains have ceased. This chapter looks into the critical aspects of hydrological drought management, exploring the multifaceted nature of this challenge and outlining strategies to mitigate its devastating consequences. We will navigate the intricate web of factors that contribute to hydrological drought, from climatic drivers to the profound influence of human activities. Understanding these causes is paramount to developing effective management approaches.

Technical Term                        Definition

Hydrology                               Hydrology is the science of water derived from Greek wordî hydro + logosî i.e., water + sciences and hance defined as the science which deals with occurrence, distribution and circulation of atmospheric water through unending Hydrologic cycle.