सिंचाई, जल निकास एवं पंपिंग प्रणाली

Calculation of Overall Farm Irrigation System Efficiency:

• Water Conveyance Efficiency ($\eta_c$):
  $$\eta_c = \frac{V_f}{V_s} \times 100 = \frac{8,100\text{ m}^3}{9,000\text{ m}^3} \times 100 = 90\%$$
• Water Application Efficiency ($\eta_a$):
  $$\eta_a = 60\% = 0.60$$
• Farm Irrigation System Efficiency ($\eta_s$):
  $$\eta_s = \eta_c \times \eta_a = 0.90 \times 0.60 = 0.54 = 54\%$$
  Alternatively:
  Water stored in root zone = $8,100 \times 0.60 = 4,860\text{ m}^3$
  $$\eta_s = \frac{4,860}{9,000} \times 100 = 54\%$$

Drainage coefficient ($D_c$) is the depth of water (in cm or inches) removed from the drainage area in 24 hours (1 day).
Discharge $Q = 0.2\text{ m}^3/\text{s}$
Volume of water drained in 24 hours:

Drainage Area $A = 250\text{ ha} = 250 \times 10,000 = 2,500,000\text{ m}^2$
Depth of water removed ($D_c$):

Classification of Subsurface Drainage Layouts:

• Herringbone System: In a herringbone layout, the central main drain is aligned along the lowest swale, depressional draw, or natural drainage depression of the field. Laterals enter the main from both sides at an acute angle (typically $45^\circ$ to $60^\circ$), resembling the skeletal spine and rib bones of a herring fish.
• Other Systems:
• Parallel system: Parallel laterals enter the main drain from one side at right angles ($90^\circ$).
• Gridiron system: Similar to parallel, but laterals enter perpendicular from both sides.
• Random system: Undulating topography where isolated wet pockets are drained randomly.