- •Unit 1. Lesson1.
- •Vocabulary:
- •Lesson 2
- •1.Прочитайте и переведите текст. Water is life.
- •Vocabulary:
- •Lesson 3
- •1.Прочитайте и переведите текст. The hydrologic cycle.
- •Lesson 4.
- •1.Прочитайте и переведите текст. The water of the Earth
- •Lesson 5.
- •1. Прочитайте и переведите текст. Hydraulics.
- •Vocabulary:
- •Lesson 6.
- •1.Прочитайте и переведите текст.
- •Vocabulary:
- •Lesson 7.
- •1.Прочитайте и переведите текст. Water in Moscow.
- •Vocabulary:
- •Lesson 8.
- •1. Прочитайте и переведите текст. The spring water of Moscow
- •Vocabulary:
- •Lesson 9.
- •Прочитайте и переведите текст. Moscow waterworks.
- •Vocabulary:
- •Lesson 10.
- •1.Прочитайте и переведите текст Where Moscow’s water flows from
- •Vocabulary:
- •Lesson 11.
- •1.Прочитайте и переведите текст. Water: Pay More, Use Less.
- •Vocabulary:
- •Lessons 12-13.
- •1. Прочитайте и переведите текст.
- •Part 1.
- •Vocabulary:
- •Vocabulary:
- •Lessons 14-15. Water Supply and sewages
- •1.Прочитайте и переведите текст.
- •Vocabulary:
- •Part 4 .
- •Vocabulary:
- •Lesson16.
- •1.Прочитайте и переведите текст. How can the Aral Sea be saved?
- •Vocabulary:
- •Lesson 17.
- •1.Прочитайте и переведите текст. Keeping the Caspian clean.
- •Vocabulary:
- •Lesson 18.
- •1.Прочитайте и переведите текст. What is to be done with the Sea of Azov.
- •Vocabulary:
- •Lesson 19.
- •1. Прочитайте и переведите текст.
- •Volga water is not sufficient
- •Lesson 20.
- •1. Прочитайте и переведите текст. Watching the ecology.
- •Text 2 Sprinkler irrigation
- •Text 3 Subirrigation
- •Text 1 The perspective and objectives of irrigation
- •Irrigation methods and their selection
- •2.1 Compatibility
- •2.3.Topographical characteristics
- •2.4. Soils
- •2.5. Water supply
- •2.6.Crops
- •2.7. Social influences
- •2.8. External influences
- •2.9. Summary
- •3.1.2 Scope of the guide
- •3.1.3 Evolution of the practice
- •3.2 Surface irrigation methods
- •3.2.1 Basin irrigation
- •3.2.2 Border irrigation
- •3.2.4 Uncontrolled flooding
- •3.3 Requirements for optimal performance
- •3.3.1 Inlet discharge control
- •3.3.2 Wastewater recovery and reuse
- •3.4 Surface irrigation structures
- •3.4.1 Diversion structures
- •3.4.2 Conveyance, distribution and management structures
- •3.4.3 Field distribution systems
- •Text 4 Advantages and disadvantages of surface irrigation
- •4.1. Advantages
- •4.2. Disadvantages
- •Text 5.
- •5.1.Objective and scope of design
- •5.2 The basic design process
- •5.2.1. Preliminary design
- •5.2.2 Detailed design
- •5.3 Computation of advance and intake opportunity time
- •5.4 Furrow irrigation flow rates, cutoff times, and field layouts
- •5.4.1 Furrow design procedure for systems without cutback or reuse
- •5.4.2 Design procedure for furrow cutback systems
- •5.4.3 Design of furrow systems with tailwater reuse
- •5.4.4 Furrow irrigation design examples
- •5.5 Border irrigation design
- •5.5.1 Design of open-end border systems
- •5.5.2 Design of blocked-end borders
- •5.5.4 A blocked-end border design example
- •5.7 Summary
- •5.6 Basin irrigation design
- •5.6.1 An example of basin design
- •Text 6. Field measurements
- •Text 7. Determining water requirements
- •Figure 2 a perspective of the on-farm water balance
- •Figure3 The perspective of water balance at the field level
- •An example problem on soil moisture
- •Text 2 Environmental problems
- •Text 3 Aral Sea- What Was and What Is
- •Is the climate warming?
- •Conclusion.
- •Glossary of terms
- •Vocabulary
5.3 Computation of advance and intake opportunity time
The difference between an evaluation and a design is that data collected during an evaluation include inflows and outflows, flow geometry, length and slope of the field, soil moisture depletion and advance and recession rates. The infiltration characteristics of the field surface can then be deduced and the application efficiency and uniformity determined. Design procedures input infiltration functions (including their changes during the season), flow geometry, field slope and length, and determine the rates of advance and recession as well as the field performance levels for various combinations of inflow and cutoff times.
The calculation of advance time is possibly the most important design step. At the beginning of the design process, this procedure is used to test whether or not the maximum flow will complete the advance phase within a prescribed time. Then it is used to find the minimum inlet discharge, and in the case of cutback or reuse systems to find the desired flow for the system operation. It is suggested that after the maximum inflow is determined and the associated tL checked, the flow be incrementally decreased and additional values of tL determined so that a relationship between flow and advance time can be established. At the end of this procedure, the minimum flow will also have been identified as that which fails to complete the advance phase in a set time, 24 hours for example. Finally, the tL computation is used repeatedly in the search for the flow which maximizes the application efficiency.
5.4 Furrow irrigation flow rates, cutoff times, and field layouts
There are three primary furrow designs:
a) furrow systems without cutback or tailwater reuse facilities; b) the cutback system; and c) the tailwater recirculation system.
These systems should be flexible to irrigate fields adequately in which the surface roughness and intake rates vary widely from irrigation to irrigation. The philosophy of design suggested in this guide is to evaluate flow rates and cutoff times for the first irrigation following planting or cultivation when roughness and intake are maximum and for the third or fourth irrigation when these conditions have been reduced by previous irrigations.
5.4.1 Furrow design procedure for systems without cutback or reuse
The application efficiency should be maximized subject to the limitation on erosive velocity, the availability and total discharge of the water supply, and other farming practices. The inflow should be reduced and the procedure repeated until a maximum Ea is determined.
5.4.2 Design procedure for furrow cutback systems
Any procedure which attempts to maximize application efficiencies will determine the minimal waste trade-off point between tailwater and deep percolation. Small values of inflow reduce tailwater losses but increase deep percolation losses. Large furrow flows advance over the field rapidly thereby providing the potential for greater application uniformity and less deep percolation, but also greater tailwater losses as the water flows from the field for a longer time.
One method of minimizing tailwater is to reduce the furrow inflow when the advance phase is completed. Most cutback systems are designed to operate in two concurrent sets, one advance phase set and one wetting or ponding; set. The advance phase and the wetting phase are both equal in duration to the required intake opportunity time. One of the most common cutback systems is that proposed by Garton (1966) and is illustrated in Figure 54. The head ditch is divided into a series of level bays with spires or other means of diverting water into the furrows. As is shown, the differences in bay elevations correspond to the head on the outlets needed to provide the desired advance phase flow and the wetting flow simultaneously.
The design procedure for the system illustrated in Figure 54 follows a sequence not entirely unlike that of the non-cutback systems but with several points of additional concern. In addition to information describing the furrow geometry, infiltration characteristics, field slope and length, and the required application, it is also necessary to know the relationship between head ditch water level and the furrow inflow: