List of top Irrigation and Drainage Engineering Questions on Groundwater Flow

A salt affected crop field is to be leached with irrigation water having salt concentration of 3.5 meq/L. Salt concentration in saturation extract of soil is 15.2 meq/L. Leaching efficiency of field = 55%. In March, ET\(_0\) = 150 mm, effective rainfall = 75 mm, crop coefficient = 1.05. Find leaching requirement for the month in mm.

A 0.30 m well penetrates an unconfined aquifer (saturated depth = 40 m). Pumping 0.03 m\(^3\)/s for 8 hours. Drawdowns in two observation wells: 3 m at 20 m, 2 m at 50 m. Find drawdown in pumping well in m.

It is planned to provide irrigation in a crop field having field capacity and permanent wilting point of the soil as 0.21 cm\(^3\)/cm\(^3\) and 0.09 cm\(^3\)/cm\(^3\), respectively. The crop root zone depth is 0.90 m. The growing period of this crop is 1\(^\text{st}\) January to 31\(^\text{st}\) March, during which the observed reference evapotranspiration (ET\(_r\)), effective rainfall (P\(_e\)) and crop coefficients (K\(_c\)) are given: \[ \begin{array}{|c|c|c|c|} \hline \text{Month} & \text{ET}_r \, (\text{mm/day}) & P_e \, (\text{mm/month}) & K_c
\hline \text{January} & 11 & 8 & 0.80
\text{February} & 12 & 25 & 1.10
\text{March} & 14 & 27 & 1.15
\hline \end{array} \] Considering management allowable deficit (MAD) for this crop as 50%, the average irrigation interval during the growing period in days is:

A sprinkler irrigation system has been designed for a crop with the water application rate of \(1.17 \,\text{cm h}^{-1}\) and sprinkler discharge of \(1.3 \,\text{L s}^{-1}\). The coefficient of discharge and uniformity coefficient are 0.9 and 0.8, respectively. If the sprinkler spacing along the lateral is 20 m, the lateral spacing in m is

The average discharge, operating pressure and emitter constant of a drip emitter are \(4\,\text{L h}^{-1}\), \(110\,\text{kPa}\) and \(0.3\), respectively. The type of emitter is

Water from a confined aquifer having transmissivity of 1000 m$^2$ day$^{-1}$ is pumped through a fully penetrating well of 300 mm diameter at a rate of 1200 m$^3$ day$^{-1}$. If the radius of influence is 400 m, the drawdown in the well under steady-state flow condition in meter is _____.

A stream of 200 L s$^{-1}$ is diverted from a canal to irrigate a wheat field in 8 hours. If the runoff from the field is 500 m$^3$ and the conveyance efficiency is 75%, the application efficiency in percent is _____.

In a subsurface drainage network, 12 lateral drains each of 100 m long are laid at a spacing of 50 m. These lateral drains are connected to a collector drain. When the water table dropped 50 cm below the soil surface in 4 days, the average discharge at the outlet of the collector drain was found to be 12 L s$^{-1$. The average drainable porosity of soil in per cent is _____.} \textit{[Round off to two decimal places]}

A sample of 90% saturated clay soil has void ratio and specific gravity of 0.8 and 2.7, respectively. The bulk unit weight of soil in N m\(^{-3}\) is __________.

A parabolic shaped grass-waterway is to be designed to carry a flow of 2.85 m³/s down the slope of 3%. The permissible velocity of water in the waterway is 1.78 m/s. If the freeboard depth is excluded, the most appropriate top width in m and depth in m, respectively are (Take Manning’s roughness coefficient = 0.04).

The ratio of soil loss from the field plot length to that from the unit plot with a slope length of 22.13 m is 0.5. If the slope length from the watershed divide is 600 m and the slope gradient is 8%, the topographic factor in the Universal Soil Loss Equation is _____. \textit{[Round off to two decimal places]}

The area of a rectangular field was measured using a 30 m survey chain, which was later found to be 5 cm short. If the length and width of the field measured using this chain were 542 m and 554 m, respectively, the true area of the field in ha is _____. \textit{[Round off to two decimal places]}

The shape of falling limb of a hydrograph is dependent on __________.

The ratio of inertial forces to viscous forces is known as __________.

Complement of the Solar Altitude angle is __________.

In construction of gravel packed wells, the pack-aquifer ratio is generally defined as __________.