eChapters

3.1 Determination of Bulk Density of Soil

3.1.1 Determination of Bulk Density of an undisturbed Soil

Bulk density of soil is expressed as the ratio of the mass (weight) of soil particle to their total volume including the pore space between the soil particles. Alternately, it is the weight of unit volume of dry soil. It is usually expressed in the unit of gram per cubic centimeter (g/cc) or mega gram per cubic meter (Mg/m³). In fine textured soil bulk density varies from 1.00 to 1.60 g/cc, whereas in coarse textured soil from 1.20 to 1.80 g/cc.

This chapter contains the description of the Indigenous Traditional Knowledge practices as subject wise manner viz, Traditional varieties, Crop management, Crop protection measures, Post harvest methods, Storage structures, Farm tools, Medicinal plants, Ethnoveterinary practices, Fisheries and others related to agriculture.

Introduction

Desert soils are the soils of arid regions that remain dry for most part of the year and support sparse xerophytes. The amount of water received by precipitation is far less than what is lost by evapotranspiration. Most deserts receive an average precipitation of less than 400 mm. Because of extreme imbalance between evapotranspiration and precipitation, many desert soils contain salts.

Distribution

Deserts occupy about one-third of the areas of Africa and Australia, 11% of Asia and about 8% of the Americas (Boul et al. 1997). Desert soils include both cold and hot desert. In India, desert soils occur in three agro-ecological regions (AER). The cold arid desert of extreme north (Leh, Ladakh region of Jammu & Kashmir ), the hot arid desert of north western India (Rajasthan, southern parts of Haryana and Punjab and northern parts of Gujarat) and the tropical arid desert of the Deccan plateau in South India represents AER 1, 2 and 3, respectively. The three different desert regions in India have characteristic climatic and soil conditions.

Introduction

Low and erratic precipitation, diurnal fluctuations in temperature and low humidity are the typical characteristics of deserts and their margins. Further, strong winds, sunny and very bright days and unpredictable periods of drought and famines are regular features. These lands are poor in fertility. Uninterrupted increase in human and animal pressures is violating carrying capacity of the natural resources, thus resultant is desertification.

Arid zones are described as a part of the drylands, and have the most severe edapho-climatic conditions. The major distinguishing feature for defining and for planning for the arid zone is the low rainfall (below 500 mm or Aridity Index <0.20) with more than 50% inter-annual variability. This makes a great difference in terms of the nature of the ecosystem, the socio-economic environment and the challenges for sustainability. High wind and solar regimes further increase the effect of rainfall variability and the whole complex makes a fragile ecosystem in which small disturbances may cause great loss to the sustainability, which are sometimes irreversible (Hou’erou, 1996). The hot arid zones of the world are economically and environmentally disadvantaged, with unique problems. The ecosystems of these zones are highly fragile with large risks that cause severe impediments to development programs. Of the total land area in the world, arid zones cover 18.8% and the hyper-arid zones account for 22.3% of the total arid zones (FAO, 1989).

Abstract

Burkina Faso is a landlocked country in West Africa with a dry tropical climate characterised by a short rainy season and a long dry season. The annual rainfall varied between 300mm in the northern part of the country to 1200mm in the meridian part. Since many years, the degradation of climatic conditions is observed. Therefore, the annual rainfalls of the 1971-1981 period were inferior to those of the precedent periods, and also the deterioration of the climatic conditions led the limits of some ishoteques “isohyète” to move southward, more than 50km farther. Furthermore, the decennial rainfalls since 1920 were subjected to a latitudinal displacement to the south. For example the ishoteque “isohyète” 500mm which were located at the North of the 15°N outside Burkina Faso during the years 1950-1960 moved gradually year by year and reached the 14°N during the years 1970-1980 inside Burkina Faso.

Abstract

Conversion of an already arid land into a desert through indiscriminate human actions magnified by droughts. Such actions include overgrazing, repeated burning, intensive farming, and stripping of vegetation for firewood. One quarter of the earth’s surface is threatened by desertification - an area of over 3.6 billion hectares. Since 1990, Six million hectares of productive land are lost every year due to land degradation. Desertification threatens the liveihoods of more than one billion people and has already made over 135 million people homeless. Desertification does not occur in linear, easily mappable patterns. Deserts advance erratically, forming patches on their borders. Areas far from natural deserts can degrade quickly to barren soil, rock, or sand through poor land management.

Concept and Definition

Desertification is a major problem in the drylands of India, affecting the way of life for its inhabitants. The problem is more severe in the arid lands in the northwestern part of the country. There have been a few numbers of definitions of the word “Desertification”. However for simplicity of its origin and meaning we would refer to two of the frequently used ones; (1) proposed in 1991 by UNEP: “Land degradation in arid, semi-arid and dry sub-humid areas resulting mainly from adverse human impact and (2) prepared for the Earth Summit at Rio, held in June 1992, for inclusion in Agenda 21, as “Land degradation in arid, semi-arid and dry sub-humid areas resulting from climatic variations and human activities. (Anonymous 1992).

Comparing two of these initial definitions, it would show that first one indicated desertification as a state of natural resources like soil and vegetation, mainly resulting from human activity while the second one included climate as a major cause. However, it reduced the emphasis of human activities as being the primary responsible factor and tried to link the possible impact of climate change on desertification. But the simplicity of the 1992 definition of desertification helped researchers to bring in sharp focus on the special environmental and socio-economic problems of the drylands.

So over the years, the key words that explains the term “desertification” has been changing or are being amended for specific purposes. This would at least mean that the problem of desertification is still debated world-wide, and its impact is not limited to some nations/regions as was presumed and discussed in first of UNCCD platforms. Therefore, as a precaution and combating this process, few catchy words like non-sustainable management, productivity, over-exploitation of natural resources, dryland livelihood, droughts are found to surround the word desertification. Earlier, some, people equated desertification with advancing boundaries of the existing desert and in India, examples of expansion / contraction of geographical boundary of Thar desert was a public debate among various researchers and planners. In the same time, some of the definitions tried to broaden its geographical scope so that greater populations suffering from adverse effects of land degradation would benefit out of various remedial measures.

Introduction

Desertification is now accepted as a major environmental issue because of the fact that 69.5 percent area of the world’s dry lands and more than 1.2 billion people in over 110 countries living in this habitat are affected by various land degradation processes. During last 20 years, researchers have focused their discussion either on a condition or a cause or a set of processes to assess different paradigms of desertification. Several studies carried out in arid western part of Rajasthan (Singh et al., 1992, Kar, A. 1993b, Kar, 1995, Dregne, H.E. 2000, Kar et al.2007) show that wind erosion is still a major problem. Though, there are many instances of location specific problems like water erosion, salinity/ alkalinity and water logging, about 75% area in arid western Rajasthan is affected by wind erosion hazard of different intensities (SAC, 2007, Kar et al. 2009). Decreasing rainfall gradient from east to west and increasing wind strength in that direction are responsible for the spatial variability in sand reactivation pattern. Water erosion in the form of sheet, rill and gully erosion is a major problem in areas, where average annual rainfall exceeds 350 mm, the rainfall intensity is high and the topographic and soil characteristics favour high run-off. Destruction of vegetation cover and excessive ploughing of shallow soils, especially on the sloping lands, accelerate the problem.

Introduction

Desertification, which is considered a major threat in the drylands of the world, is not about advancing boundaries of the existing deserts, but about land degradation in the arid, semi-arid and the dry sub-humid regions, which together form the drylands (Anon., 1995). Secular variation in climate that has resulted in periodic expansion and contraction of the desert boundaries and regional-scale changes in vegetation condition (Tucker et al., 1991; Nemani et al., 2003; Hickler et al., 2005) is one of the drivers of desertification. Human activities constitute the other major driver. According to Geist and Lambin (2004) the prominent core variables that drive degradation are climatic, economic, institutional, national policies, population growth and remote influences.

We let you know that the type of people in a given region is closely linked to the kind of resources found in the concerned region; and which are necessary for human beings to survive.

In fact, more than 100 countries possess arid lands, where more than 40% of the global population lives. The soils of these regions present too much fragility and they are too degraded that they can’t allow people to survive.

Let’s emphasize that in Africa, two third of the total area are arid zones. Thus, for Africans, the type of their struggle for adaptation to the context of their land, illustrates their ingenious capacity to model their hostile surroundings and to leave marks of their cultures all over prehistory and history.

Social organizations in those arid areas are closely linked to modes of exploitation and valuation of resources (water and land). However, human productions in those areas are doubly menaced; on one side by the action of humans who exploit resources for their immediate needs, and on the other side, by climate adverse effects during long periods of drought. It means that climate change and violent meteorological phenomenon worsen circumstances. That leads to environmental degradation and biodiversity reduction; alarming deterioration of vital conditions; and intensification of poverty, both in rural and urban areas; particularly among women and young. Consequently, there are non durable (viable) agricultural practices, overexploitation, overgrazing, excessive and illegal forestry exploitation; destruction of forests and bushes by non-controlled fires, pillages and conflicts with weapons; reduction of vegetation, due to the scarcity of rain; of water in general and menaces of heaps of sands.

1.0 General

 The design of canal involves following three major aspects:

 A Irrigation and drainage canal network planning.

 B Determination of discharge / capacities of  canals and drainages.

 C Determination of shape and size i.e. geometrical dimensions of the proposed canal section, generally

 known as design of canal section. More appropriately it can be called as design of internal section

 of canal. It can be further divided in three following parts viz.

 i. Design of unlined canals:

 ii. Design of lined canals: or a canal may be partly lined and partly unlined.

 iii. Choice between the unlined and lined canals. This aspect should be distinguished from the selection of type of lining. However, the scope of choice of lining may include both the aspects.

 The design of canal section remains incomplete without the design of its embankments, either in lined or unlined canal, so the next aspect is

 iv. Design of canal embankments. Still to complete the design of a canal one more aspect is required i.e.

 v. Canal aesthetics and canal arboriculture.

Designing an earthen dam requires the coordinated evaluation of catchment runoff, reservoir capacity, site conditions, foundation properties, expected service life, and the consequences of failure. A selected return period is used to estimate extreme rainfall and runoff, while adequate spillway capacity and freeboard protect the embankment against overtopping. The dam must possess low permeability, stable upstream and downstream slopes, and sufficient resistance to seepage, settlement, erosion, and earthquake forces. This chapter presents design criteria, top width, dam height, side slopes, freeboard, seepage-control components, slope-protection measures, and stability considerations. It also explains procedures needed to create a safe, economical, and functional embankment.

A canal of approximate discharge of less than 80 cumecs (3000 cusecs) discharge may be called a medium or low capacity canal).

3.1 Mehboob Section

A Mehboob Section is only a modification of best trapezoidal section by making its complete bottom circular as shown in figure 3.1. Also see figure 1.6 and para 1.7. That is why these canals are also known as canals of zero bed width, or trapezoidal canals with curved bottom, or cup shaped canals.

But these cannot be called as triangular canals with curves, as often spoken. In fact it is a truncated triangle circumscribing the semi circle. Trapezium is also a truncated triangle circum scribing a circle.

More accurately it can be said as a combination of semi circular and best trapezoidal section so as to take full advantage of their hydraulic efficiency and practicability.

This is such a beautiful section that the designer can never commit a mistake, even if he wants to commit a mistake. The dimensions are so geometrically fixed that no one can play with any dimension.

The value of this section was realised for the first time by Er S I Mehboob (1943) in his Punjab Irrigation Branch Paper No.260" Lining of Canals". There after this canal section became well known as Mehboob Section after his name. He also stated that the most economical section i.e. the maximum area for the minimum perimeter is when the centre of the arc is at the full supply line of the section. This is also evident in figure 1.6. This is also the condition for all best hydraulic sections. This section is also useful to a higher silt carrying capacity than a wide shallow one..

Abstract

The paper presents the innovation of solar tunnel dryer; it is a walk in type semi-cylindrical poly house framed structure with UV-stabilized polythene sheet, where products on large scale could be dried under controlled environment. Chilly drying in solar tunnel dryer to reduce the moisture content from 83.4 % (w.b.) to about 9 % (w.b.) and Aonla pulp from moisture content of 81 %(w.b.) to safe moisture content 9.5 %(w.b.) successfully dried. 20-30^ºC of higher temperature was obtained in solar tunnel dryer over the ambient temperature, depends on product. In comparison to open sun drying to obtain the same level of moisture contents resulting in a net saving in drying time of 40-50% for solar tunnel dryer over open sun drying.

A. Rectangular Canals

5.1 Design of Best Rectangular Canals

After the Mehboob and Trapezoidal canals, next best section is rectangle. This section is also generally adopted for small discharges say upto 10 cumecs (350 cusecs). This section ranks at No. 4. Yet, this is the only section most commonly adopted for flumes of discharges upto140 cumecs (5000 cusecs). Typical example is Orsang acqueduct, 1 km. long for 1140 cumecs (40000 cusecs) in ractangular sections on Narmada Canal Project, Gujrat, India, built in the years from 1990 – 2000. Such sections are common in power house canals due to limitation of space and very sharp curves. It is free from the effect of change of side slopes as in the trapezoidal canals (see para 3.3) Still some small side slope (batter) is adopted in thick masonry / concrete lining. It adds to structural stability with economy in thickness of wall and as well as hydraulic efficiency. It may still be called as rectangular section.

Details of its hydraulic efficiency in comparison to semi circle, Mehboob and trapeziodal sections are discussed in chapter 1, para 1.8

The pipe network in a drip system consists of a mainline, sub mains, laterals, and distributors. The layout of the pipes depends on the physical factors like shape and size of the area, topography and any other obstacles in the field. In any field there may be the scope of different layout of the pipes. The most economic one should be selected. In general, contour line is followed in laying the laterals in sloping land, sub main length usually be shorten in uphill and equally spaced laterals on either side of a sub main in a flat land provides good layout.

Hydraulic Formulae /Head Losses in Pipes

There are numerous equations for solving the head loss in pipes. The most commonly used are the Darcy-Weisbach, Hazen-William and Scobey’s.

A canal of more than 80 cumecs (3000 cusecs) approximetly may be called as a high capacity canal.

It has already been pointed out in chapter 1, that for the best section of any shape, R is always equal to d/2 only, and such depth is the most optimum depth. But such channels are not always practical or most economical due to many other practical reasons, (see para 4.1 and 6.3) and many times shallower depth then this depth is adopted. Typical examples are lining of existing earthen channels, given in para 6.3.

All the best sections have fixed ratio of dimensions very near to the semi circle. For large discharges, radius of semi circle increases that, means depth of canal as well as velocity increases. But higher velocity is not permissible with every type of lining (see table 2.1 and para 2.3). Similarly depth also has limitation of construction, maintenance, stability of slopes, etc. see example–4.2.

Because of limiting velocities and depth, deeper canal section are not practically feasible/possible. Therefore for large discharges, say more than 100 cumecs, Mehboob or best trapizodal sections are just not possible/practical, and recourse has to be taken to trapezoidal section with increased bed width then depth. This section is hydraulically inefficient or uneconomical. Larger the B/D ratio, larger is the inefficiency and section is more costly. (For Mehboob Section, B:D ratio is zero and for best trapizodal section it is much less than 1, see para 3.1, table 3.1 para 3.5 and table 3.4).

Kaushik Kumar

Design Thinking

Design thinking has emerged as one of the skill set in the recent competitive environment.Basic science has been mainly involved in development of various models that fulfills the requirements of engineering domain.

However, the engineering graduates being produced did not possess the required industrial skills and hence were perceived by academia and industrialists as ineligible to be employed in various industries.