(SEM VII) THEORY EXAMINATION 2022-23 SOIL & WATER CONSERVATION ENGINEERING

SECTION A (2 Marks Each)

(a) Effect of Soil Erosion

Soil erosion removes fertile topsoil, reduces soil productivity, lowers crop yield, increases flooding, and causes siltation in rivers and reservoirs.

(b) Spillways

A spillway is a structure provided in dams or embankments to safely dispose excess water without damaging the structure.

(c) Classification of Gullies

Gullies are classified as V-shaped gullies, U-shaped gullies, and box-shaped gullies based on their cross-section.

(d) Factors Responsible for Sheet Erosion

Rainfall intensity, slope of land, soil type, lack of vegetation cover, and land use practices cause sheet erosion.

(e) Impact of Surface Roughness on Wind Erosion

Greater surface roughness reduces wind speed near the ground and decreases wind erosion, while smooth surfaces increase erosion.

(f) Methods of Air (Wind) Erosion Control

Wind erosion can be controlled by shelter belts and strip cropping.

(g) Methods of Grassland Management

Methods include controlled grazing, rotational grazing, reseeding, fertilization, and weed control.

(h) Types of Water Losses

Water losses include evaporation losses, seepage losses, transpiration losses, and percolation losses.

(i) Infiltration

Infiltration is the process by which water enters the soil surface and moves downward into the soil profile.

(j) Soil Conservation

Soil conservation is the protection and management of soil to prevent erosion and maintain soil fertility.

 SECTION B (10 Marks Each – Any Three)

(a) Annual Soil Loss Using USLE

The Universal Soil Loss Equation is
A = R × K × LS × C × P

Given:
R = 800, K = 0.20, LS = 0.2, C = 0.50, P = 1.0

Soil loss,
A = 800 × 0.20 × 0.2 × 0.50 × 1.0
A = 16 tons/hectare/year

When contour farming is adopted, P = 0.5
A = 800 × 0.20 × 0.2 × 0.50 × 0.5 = 8 tons/hectare/year

Percentage reduction in soil loss
= (16 − 8) / 16 × 100
= 50% reduction

(b) Difference Between U-Shaped and V-Shaped Gullies

V-shaped gullies are deep and narrow with steep sides, usually formed in cohesive soils.
U-shaped gullies are wide and shallow with gentle side slopes, commonly formed in less cohesive soils.

(c) Biological Methods of Soil Conservation

Biological methods include afforestation, strip cropping, contour farming, crop rotation, grass planting, and cover crops. These methods protect soil naturally by reducing runoff and wind velocity.

(d) Agricultural Waste Contamination of Water Sources

Agricultural waste such as fertilizers, pesticides, and animal waste pollute water bodies, causing eutrophication, toxicity, and degradation of water quality.

(e) Need for Planning of Water Resources Projects

Planning ensures optimal utilization of water resources, flood control, irrigation supply, power generation, environmental protection, and long-term sustainability.

SECTION C (10 Marks Each)

Q3

(a) Why Erosion Rates Are Higher in Clay Soils

Clay soils have fine particles that detach easily when saturated. Poor drainage causes runoff, leading to higher erosion compared to sandy soils which allow quick infiltration.

(b) Wind Erosion Control Measures

Wind erosion is controlled by shelter belts, strip cropping, surface roughening, mulching, maintaining soil moisture, and planting wind-resistant crops.

Q4

(a) Contour Bund Design (Conceptual Answer)

Contour bunds are designed based on rainfall excess, land slope, horizontal interval, and weir flow depth. The bund height is calculated to safely store runoff, while cross-sectional area ensures stability and prevents overtopping.

(b) Components of Chute Spillway

Components include inlet channel, chute or trough, energy dissipator, side walls, and outlet channel.

Q5

(a) Assessment of Surface Water Resources in India

India’s surface water resources come from rivers, lakes, reservoirs, and rainfall runoff. Inter-basin development transfers water between basins, while intra-basin development optimizes water use within a basin.

(b) Soil Quality Management and Reclamation of Salt-Affected Soils

Soil quality management involves improving physical, chemical, and biological properties. Methods include organic matter addition, crop rotation, and balanced fertilization.
Salt-affected soils are reclaimed by leaching, gypsum application, drainage improvement, and growing salt-tolerant crops.

Q6

(a) Processes Involved in Water Self-Purification

The four processes are dilution, sedimentation, oxidation, and biological decomposition.

(b) Control and Reduction of Evaporation Losses

Evaporation losses are reduced by windbreaks, chemical films, floating covers, and reducing exposed water surface area.

Q7

(a) Measures for Flood Control

Flood control measures include dams, embankments, floodways, channel improvement, watershed management, and afforestation.

(b) Economic Importance of Water Resources

Water resources support agriculture, industry, power generation, transportation, fisheries, domestic supply, and overall economic development.