If the soil of the canal bed is porous and coarse grained, it leads to more seepage loss and consequently low duty. If it consists of alluvial soil, the percolation loss will be less and the soil retains the moisture for longer period and consequently the duty will be high.... When the

The factors which affect the selection of suitable type of cross drainage works are: 1. Relative bed levels and water levels of canal and drainage. 2. Size of the canal and drainage. 3. When the bed level of the canal is much above the HFL of the drainage, an aqueduct is the obvious choice. 4. When the bed level of the drain is well above FSL of canal, super passage is provided

The maximum discharge capacity and the number of spillways are determined by studying the following factors: By studying the flood hydrograph of past ten years, the maximum flood discharge may be computed which is to be disposed off completely through the spillways. The water level in the reservoir should never be allowed to rise above the maximum pool

The height of the dam is always fixed according to the maximum reservoir capacity. The normal pool level indicates the maximum capacity of the reservoir. The water is never stored in the reservoir above this level. The dam may fail by over turning so, for the safety of the dam the spillways are essential. The top of the dam is generally utilized by making road.

The topography, hydrology, hydraulics, geology and economic considerations all have a bearing on these decisions. For a given inflow flood hydro graph, the maximum rise in the reservoir level depends on the discharge characteristics of the spillway crest and its size and can be obtained by flood routing. Trial with different sizes can then help in getting the optimum combination