GATE 2014, PSUs- irrigation Engineering - one liners - part 11

Hello there,

Here is the 11th part of our notes for the preparation of the GATE and PSUs exams.

• Fertility of a soil is adversely affected, when the pH value is more than 11.
• Optimum depth of kor watering for rice crop is nearly 19 cm.
• Average delta of rice crop is nearly 120 cm.
• The duty of a crop is 432 hectares/cumec, when base period of the crop is 100 days. Delta for the crop will be 200.
• Water consumed in irrigation, when compared with the total water used for all purposes in our country, is about 90%.
• Water consumed for producing one tonne of wheat and one tonne of rice will be of order 2000 tonnes and 4000 tonnes.
• Lime concrete lining is used when velocity of flow is below 2 m/sec, irrigation channel with capacity upto 200 cumec and where economy is required.
• Thickness of concrete lining, for discharge upto 200 cumec varies from 10 to 15 cm.
• Force considered for the analysis of an elementary profile of a gravity dam under empty reservoir condition is self weight.
• Uplift pressure on a dam can be controlled by pressure grouting in foundation, constructing drainage channels between dam and its foundation and by constructing cut-off under upstream face.
• In a gravity dam total force due to wave pressure acts at a height of 0.375.hw above the still water level.
• Horizontal acceleration due to earthquake results in hydro-dynamic pressure and inertia force in the body of the dam.
• Vertical acceleration due to earthquake results in increase in the effective weight of the dam and also decrease in the effective weight of the dam.
• In the elementary profile of a dam having empty reservoir condition, vertical stress at heels and toe are respectively given by 2W/B and 0.
• In gravity dam, main overturning force is water pressure.
• For economical design of a gravity dam, shear friction factor should be 0.65.
• In Ogee shaped spillway, discharge is proportional to H^(3/2).
• Garrets diagrams are based on Kennedy's theory.
• Discharge co-efficient of an Ogee-shaped spillway is 3.7.

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