A reservoir has a total capacity of 25 million cubic metres and a dead storage of 5 million cubic metres. Given an average sediment deposition rate of 0.10 million cubic metre per year, the useful life of the reservoir will begin to decline after_________________?
Show answer Hide answer
Answer: A. 50 years
Explanation
Dividing the dead storage capacity by the annual sediment rate gives the time before useful storage declines. Five million cubic meters of dead storage divided by zero point ten gives exactly fifty years. Once sediment fills the dead storage space, further deposition begins encroaching into useful storage. Reservoirs lose storage capacity over time due to continuous sediment deposition from inflowing rivers. Dead storage is the reservoir volume reserved below the lowest outlet level for sediment accumulation. Sedimentation surveys help dam operators monitor capacity loss and plan long term mitigation strategies.
Reservoir lifespan planning is critical for regional water supply and hydroelectric power sustainability. Sediment accumulation reduces the economic viability and flood control capacity of aging dams. Watershed conservation measures are implemented upstream to reduce soil erosion and reservoir sedimentation rates. Option b overestimates the lifespan by miscalculating the available dead storage volume. Options c and d represent incorrect arithmetic calculations or confuse total capacity with dead storage. Incorrect options fail to isolate the specific dead storage volume dedicated to trapping sediment.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. The proportion of the volume of water stored within the crop root zone to the volume of water actually supplied to the field is termed as__________________?
Show answer Hide answer
Answer: B. water application efficiency
Water application efficiency compares the water stored in the root zone to the water delivered to the field. It directly reflects how well irrigation practices avoid deep percolation losses below the root zone. Higher ap...
Q2. At a certain point, a river stage carrying a discharge of Q m7sec is 10 m with a water surface slope of (1/4000). The flood discharge at this very location for the same stage of 10 m when the water surface slope becomes (l/1000) will be________________?
Show answer Hide answer
Answer: C. 2 Q m3/sec
Using Manning equation, discharge is proportional to the square root of the water surface slope. Multiplying Q by the square root of (1/1000 divided by 1/4000), which is the square root of 4, gives 2Q. The doubling of th...
Q3. The ratio of the mean shear stresses generated on the bed versus the banks of an open channel driven by flowing water is________________?
Show answer Hide answer
Answer: C. greater than 1
Mean shear stress on the bed of an open channel is typically greater than that on the side banks. Side wall friction reduces the effective shear stress acting on the bank boundaries. Hydraulic boundary distribution analy...
Q4. A stream that lacks any base flow contribution is designated as________________?
Show answer Hide answer
Answer: C. ephemeral stream
Ephemeral streams carry water only briefly in direct response to immediate precipitation events. They lack any continuous base flow contribution from underlying regional groundwater tables. Their streambeds lie well abov...
Q5. Moisture that can be utilized by plants is primarily present in soils in the form of________________?
Show answer Hide answer
Answer: B. capillary water
Capillary water held in soil pores against gravity is the primary form of moisture utilized by plants. Plant roots exert suction forces that easily overcome capillary tension to extract water from soil matrices. This moi...
Q6. Useful storage refers to the volume of water held inside a reservoir positioned between________________?
Show answer Hide answer
Answer: B. minimum pool level and normal pool level
Useful storage is the operational reservoir volume located between the minimum pool and normal pool levels. Water within this zone can be withdrawn by gravity or pumping for irrigation and water supply. It represents the...