Jawaharlal Nehru Technological University Hyderabad B.Tech III WATER SUPPLY ENGINEERING Previous Question Paper (September 2021 - R16)

The per capita demand of water is the average daily volume of water required per person in a community, calculated as the total annual consumption divided by the population and 365 days. Several critical factors influence this demand:

• Size and Nature of the City: Larger cities with higher standards of living and industrial activity typically exhibit higher per capita demand compared to smaller towns or rural areas.
• Standard of Living: Economic status directly correlates with water usage. Higher income groups tend to use more water for amenities like air conditioning, dishwashers, swimming pools, and extensive gardening.
• Climatic Conditions: In hot and dry regions, water demand increases significantly due to higher requirements for drinking, bathing, and lawn irrigation. Conversely, colder regions may see lower demand.
• Industrial and Commercial Activities: The presence of water-intensive industries or large commercial hubs increases the total water requirement, which is often averaged into the per capita figure.
• Quality of Water Supply: If the supplied water is of high quality and reliable, consumption tends to be higher. Poor quality or intermittent supply often leads to wastage or reliance on alternative, less efficient sources.
• System Pressure: Higher pressure in the distribution network increases the discharge from taps and leads to greater leakage losses, thereby increasing the total demand.
• Metering and Pricing: The implementation of water meters and volumetric pricing structures encourages conservation and discourages wastage, effectively reducing per capita demand.
• Efficiency of the Distribution System: Significant water losses due to pipe leaks, burst mains, and unauthorized connections contribute to a higher 'per capita' demand, as the total water pumped must account for these losses.
• Habits and Customs: Cultural practices, such as the frequency of bathing or the use of water for religious or social rituals, influence the daily consumption patterns of the population.

To estimate the population for the year 2041, we first calculate the increments and growth rates based on the provided data:

Average increase (x) = 51250. Average percentage increase (r) = 27.78%. Average increase in percentage (r') = 0.00%.

1. Arithmetic Increase Method: Formula: P_n = P + n*x, where n = 3 decades (2011 to 2041). P₂₀₄₁ = 325000 + 3 * 51250 = 478750.

2. Geometric Increase Method: Formula: P_n = P * (1 + r/100)ⁿ. P₂₀₄₁ = 325000 * (1 + 0.2778)³ = 325000 * 2.086 = 677950.

3. Incremental Increase Method: Formula: P_n = P + n*x + [n(n+1)/2] * r'. Here r' = (5 + 3.33 - 8.33) / 3 = 0. P₂₀₄₁ = 325000 + 3 * 51250 + 0 = 478750.

Comments: The Arithmetic Increase method provides the lowest estimate, suitable for older, saturated towns. The Geometric Increase method provides the highest estimate, reflecting rapid expansion typical of developing urban areas. The Incremental Increase method provides a balanced approach by accounting for the changing rate of growth, though in this specific data set, it yields the same result as the arithmetic method due to the net zero change in growth rate.