HYDROLOGY QUIZ 2

Water Demand

the quantity of water that is needed by the population to be covered. The water to be supplied should be sufficient to cover both existing and future consumers. In addition to the projected consumptions, an allowance for non-revenue water (NRW) that may be caused by leakages and other

Level I (Point Source)

This level provides a protected well or a developed spring with an outlet, but without a distribution system. The users go to the source to fetch the water. This is generally adaptable for rural areas where affordability is low and the houses in the intended service area are not crowded. A ___________facility normally serves an average of 15 households within a radius of 250 meters.

Level II (Communal Faucet System or Stand Post)

This type of system is composed of a source, a reservoir, a piped distribution network, and communal faucets. Usually, one faucet serves four to six households within a radius of 25 meters. It is generally suited for rural and urban fringe areas where houses are clustered in sufficient density to justify a simple piped system. The consumers still go to the supply point (communal faucet) to fetch the water.

Level III (Waterworks System or Individual House Connection)

This system includes a source, a reservoir, a piped distribution network, and individual household taps. It is generally suited for densely populated urban areas where the population can afford individual connections.

Minimum day demand

the minimum amount of water required in a single day over a year.

Average day demand

the average of the daily water requirement spread in a year.

Maximum day demand

the maximum amount of water required in a single day over a year.

Peak hour demand

the highest hourly demand in a day.

Design Period

the span of time in which the initial capital outlay and succeeding outlays for expansion and rehabilitation can be rationally recovered.

Design Population

the targeted number of people that the project will serve.

Population Growth Factor

expressed as: PGR = (1 + annual Pop. Growth)"

Water Consumption

water demand expressed in per capita consumption per day. The common unit is in liters per capita per day (Ipcd).

Non-Revenue Water

the amount of water that is produced but not billed as a result of leaks, pilferages, free water, utility usages, etc. The water demand projection should assume that the NRW of the new system will be fifteen percent (15%) of the estimated consumptions. The plan's figure can be increased up to a total of 20% at the end of 10 years. These assumed NRW figures require good maintenance of utilities, pro-active leakage prevention, and no illegal connections for 100% recovery of supplied water.

Water Resources

After the demand has been estimated, the next step is to look for a source that passes both the quantity and quality requirements.

Rainwater

a product of water vapor that has risen due to evaporation and accumulated in the atmosphere, which condenses and falls on the Earth's surface. As the water vapor that has accumulated in cloud formations condenses, it forms drops of rain that fall to the Earth.

Surface Water

is exposed to the atmosphere and subject to surface runoff. It comes from rains, surface runoff and groundwater, and includes rivers, lakes, streams, ponds, impounding reservoirs, seas, and oceans. The quantity of surface runoff depends on a large number of factors; the most important of which are the amount and intensity of rainfall, the climate and vegetation, and the geological, geographical, and topographical features of the catchment area. The quality of _________ is determined by the amount of pollutants and contaminants picked up by the water in the course of its travel. While flowing over the ground, _______ collects silt, decaying organic matter, bacteria and other microorganisms from the soil. Thus, all ________ sources should be presumed to be unsafe for human consumption without some form of treatment.

Groundwater

the portion of rainwater which has percolated beneath the ground surface to form underground deposits called aquifers. The upper surface of groundwater is the water table. Groundwater is often clear, free from organic matter and bacteria due to the filtering effect of soil on water percolating through it. However, groundwater almost always contains minerals dissolved from the soil. Groundwater is often better in quality than surface waters, less expensive to develop for use, and usually provides more adequate supply in many areas in the country.

Spring

is a point where groundwater flows out of the ground and is thus where the aquifer surface meets the ground surface. A ____ may be ephemeral (intermittent) or perennial (continuous). ___ can be developed by enlarging the water outlet and constructing an intake structure for water catchment and storage.

Well

is a hole constructed by any method such as digging, driving, boring, or drilling for the purpose of withdrawing water from underground aquifers. ____ can vary greatly in depth, water volume and water quality. ____ water typically contains more minerals in solution than surface water and may require treatment to soften the water by removing minerals such as arsenic, iron and manganese. Well water may be drawn by pumping from a source below the surface of the earth. Alternatively, it could be drawn up using containers, such as buckets that are raised mechanically or by hand.

Infiltration Well

_____ galleries are horizontal wells, constructed by digging a trench into the water-bearing sand and installing perforated pipes in it. Water collected in these pipes converges into a "well" from which it is pumped out.

Rainwater

_____ would be an immediate resource to augment the existing water supply systems by "catching water wherever it falls". ______can be utilized as an important source of water supply in areas where rain is well distributed throughout the year and where surface and groundwater are scarce.

Spring Springs are outcrops of groundwater that often appear as small water holes or wet spots at the foot of hills or along riverbanks. To obtain satisfactory water, it is necessary to find the source, properly develop it, eliminate surface water intrusion, and prevent animals from gaining access to the spring. There should be no immediate upstream settlements, as these would pose the risk of biological contamination.

Infiltration Wells

involves a simple means of obtaining naturally filtered water. It consists of a system of porous, perforated, or open-joint pipe or other conduit that drains to a receiving well. The pipe is surrounded by gravel and is located in a porous formation such as sand and gravel below the water table. The collecting system should be located 6 m or more from a lake or stream or under the bed of a stream or lake. It is sometimes found desirable, where possible, to carefully place a cofferdam, cutoff wall, or puddle clay dam between the collecting conduit and the lake or stream to form an impervious wall. It is not advisable to construct an infiltration well unless the water table is relatively stable and the water intercepted is free of pollution. The depth of the collecting pipes should be about 3 m below the normal ground level, and below the lowest known water table, to assure a greater and more constant yield.

Surface Water

supplies include water from streams, rivers, lakes, ponds, seas and oceans. ______ usually contains organic and inorganic minerals and needs expensive water treatment. Unless _____ is the only option, ______ should be avoided for rural water supplies.

Production Well

is a hole which has been dug, bored, driven or drilled beneath the ground for the purpose of extracting ground water. The first step in considering the use of wells as the sources of water supply is to calculate the total capacity of the existing wells and compare this capacity to the demand for water based on the population to be served. The supply-demand analysis shows whether the existing wells can still be utilized or if new wells are needed.

Utilize Existing Well

If wells already exist, they should be checked for capacity and water quality. Wells that have the desired capacity and water quality should be given priority in selection. If capacity of a well is not sufficient, it should be checked to see if it can be developed to improve the yield. If water quality is the problem, a decision has to be made whether to go for a new well or to provide some treatment facilities.

Unsaturated zone

lies immediately beneath the ground surface and contain both water and air in the voids and pores.

Saturated zone

where the voids are all filled with water. Water in the saturated zone is referred to as groundwater or aquifer.

Water table

the boundary between the unsaturated zone and the saturated zone. The ____ is not stationary. It moves up during rainy season when percolation is high and moves down during dry season when groundwater discharge is higher. In general, the shape of the ______ tends to follow the topography of the land.

Unconfined / Water Table Aquifer

its upper limit is the water table. _____ are often shallow and the hydraulic pressure at its surface water level or water table is equal to atmospheric pressure.

Confined / Artesian Aquifer

it is sandwiched between an upper impermeable layer and a lower impermeable layer.

Shallow wells

Generally, a well is considered ___ if it is less than 20 meters deep. ______ tap the upper water-bearing layer underground. This permeable layer, however, usually has limited safe yield due to its great dependence on seasonal rainfalls. Therefore, the supply capacity of ______ could be unreliable and sometimes intermittent. Also, the water extracted from the upper strata is usually more affected by contamination since the aquifer being tapped is near the ground surface where possible sources of contamination abound. Protection against contamination is therefore one of the main considerations in constructing a ____

Deep wells

which are over 20 meters deep, tap the deeper unconfined aquifer. This aquifer is not confined by an overlying impermeable layer and is characterized by the presence of a water table. A deep well is less susceptible to surface contamination because of the deeper aquifer. Also, its yield tends to be more reliable since it is less affected by seasonal precipitation.

Artesian wells

are much like the deep wells except that the water extracted is from a confined aquifer. The confining impermeable layers are above and below the aquifer. Groundwater recharge enters the aquifer through permeable layers at high elevations causing the confined groundwater at the lower elevations to be under pressure. In some cases, the hydraulic pressure of the aquifer is sufficient for a well to flow freely at the well head.

Estimated Well Yield

the quantity of water the well can produce