Design choices, Design 1 Engineering construction methods, Water methods at Sandhikhola

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Design choices, Design 1: Engineering construction methods, Water methods at Sandhikhola

Sandhikhola village in Nepal has had water shortages over the past decade, specifically, in the dry (pre-monsoon) seasons, resulting to the drying up of ground water. Consequently, villagers have been forced to collect water from waterways situated in remotely situated streams. The Nepalese women have had to collect water for nearly four hours each day. Several water design methods proposed for the village include rainwater harvesting tanks in the local homes and spring intake structures for directing water from groundwater springs to the local tap stands. In designing and constructing the community water systems, the sources of water supply should be considered to allow for little maintenance for operational factors needed to provide sufficient supply of water to the community (Igdata 8). Several options are available namely, surface water, up-ground reservoirs or tanks.

Surface water

Surface water sources in Sandhikhola village include the tributary streams and artificial reservoirs. In regards to water protection, the water quality should be considered while examining the surface water due to pollution. This is because it may render the accessible water unusable for purposes of potable water supplies, despite provision of complete treatment (WorldBank 13.1).

Protection of the surface water should start from assessment of the water quantity. This includes reviewing the available water supply yield. The assessments should show that a minimum drought return period of one in 50 years has been applied in calculation of safe yield. The minimum drought duration of 30 days should also be used. The yield should also be sufficient to offer ample water for the authorised users of the source. The yield should also be adequate enough to meet the current and future water demands of the village without substantially affecting the waterway habitat.

The underlying impact includes provision of sufficient water for the village, relative to the population. Compared to up-ground reservoirs or tanks, surface water from the streams in Sandhikhola village is not readily available.

Up-ground reservoirs or tanks

Ground water sources can be harnessed to pump water directly to the small reservoirs or tanks, holding basis and aerial- and ground-level storage tanks. An up-ground reservoir refers to a storage facility that holds water during the periods of high stream flow or good water quality. Water is pumped into the facility for future use by the community (WorldBank 13.1). The reservoir should be constructed to ensure that high quality water is protected through control of runoff into the reservoir. Dikes should as well be constructed to be structurally fit and protected from erosion of wave action. Further, the point of influent flow should be separate from the withdrawal point. Additionally, separate pipes should be provided for influent into the reservoir and effluent out of the reservoir. In preparing the site for the reservoirs, bushes and trees should be eliminated to facilitate elevation of water. The reservoirs should have ladders and access ways to offer safe maintenance. They should also have lightning arrestors.

In planning for groundwater supply, not much can be done to determine the chemical quality of the water since the water is to be obtained from a range of well-define and varied water-bearing strata of geological layers. The water’s mineral or chemical quality from the aquifers depends on the materials that dissolve within the aquifer.

Overall, the constructions will ensure sustained high quality of water for the Sandhikhola village residents. Compared to surface water in Sandhikhola village, groundwater is considered the source of water that is mostly readily available, since it can be tapped from underneath the water table.

Water Wells

A well refers to a hole that has been drilled or dug beneath the earth surface for purposes of groundwater extraction (WorldBank 7.1). The dug wells would be a suitable source of public water supply, since the site-specific conditions at Sandhikhola village in Nepal permit its construction. Dug wells consist of pits or holes dug into the ground, mostly up to 15 metres deep, to harvest water from the water table. For protection, the dug well should be lined with bricks, concrete or stones. An underlying impact is that it prevents likely caving in of the wall. In the deep aquifer layer, walls should be aligned with prefabricated caisson rings or slots to allow groundwater to pass to the dug well.

A watertight cover should be provided at all times. Additionally, protective lining and grouted depth of not less than 3 metres from the ground elevation shall be constructed. The pump discharge piping will not be placed through the well’s wall or the wall casing. These will protect the well opening from the entry of foreign particles (WorldBank 7.1).

For sandstone or limestone wells, permanent casing will be seated firmly in the un-creviced rock, where the deepness of unconsolidated aquifers is at least 15 metres. In cases where the depth of the unconsolidated aquifers is less than 25 metres, the depth of the casing will be at least 15 metres. For naturally flowing wells, the flow should be controlled. Additionally, permanent casing should be provided. In case of erosion of the enclosing beds seems likely, protective construction will be required. This will prevent the walls from eroding.

Groundwater springs

Sandhikhola village has springs that require protection. Springs consist of outcrops of groundwater that resemble water holes or wet spots situated along river banks. To ensure that the villagers benefit from satisfactory water, the available springs should be developed and surface water intrusion eliminated. Livestock and rodents should also be prevented from accessing the springs. Additionally, no immediate upstream settlement should be allowed as it is a risk factor for biological contamination. For the springs in Sandhikhola village to be protected from surface water pollution, a deep diverting ditch should be constructed around the spring. Additionally, the collecting basin and the spring should have water-tight lid, specifically concrete.

Construction of the spring is essential, since it facilitates optimal benefits from water flow. It also prevents pollution and animal intrusion. Additionally, it prevents damage and likely diversion. In the construction process, the eye should be enlarged to increase the water yield quantity. This is attained by digging out the area that surrounds the hole, down to the impermeable layer to eliminate mineral matter, silt and rock fragments. Stones should afterwards be piled to provide foundation layer for the spring box. Later, a spring box should be constructed to surround the spring’s expanded eye. This will protect the water from contamination. Since Sandhikhola village has several springs distributed in the same area, a silt trap should be constructed to serve as the reservoir that collects water from the springs.

Rainwater

Rainwater is essentially an instant resource capable of augmenting Sandhikhola village’s existing water supply systems. This is due to the fact that rain is evenly distributed across the year while ground and surface water is scarce. Rainwater can be collected from the roofs of houses in the village before being channelled to a storage tank or cistern, which is a watertight tank. Since the rainwater is likely to wash air pollutants, paint, animal and bird dropping, leaves, as well as dirt and dust from its catchment area on the way to the cistern, special provisions should be provided to avoid the first five or ten minutes of rainwater flow, as well as to sieve the collected water. The cistern should be treated after each rainwater collection, using chlorine compound of no less than 5 mg/l chlorine. Compared to spring water, the rainwater is less reliable in Sandhikhola village.

Design 2: Education programme

The education programs should educate the villagers on the underlying factors that affect the water quality. Increased awareness can trigger increased community cooperation towards collaborative protection of the water sources (FEMA 26). Essentially, the factors that affect the water quality in the water supply system include the quality of treated water that is fed into the water supply system. Others include the materials and conditions of the water pipes, the storage facilities that form the water system, as well as, the period water is retained in the water system (Env.Gov 3-5).

Community consultation workshops should be initiated to educate the local community about the importance of monitoring the spring discharge, local stream flow and the rainfall patterns. Provision of training to the residents of the Sandhikhola village in hydrological monitoring for the already installed rainfall and stream flow gauging stations will ensure adequate protection of the engineered water systems. The community is likely to gain insight into balancing use of the spring water, rainwater, stream water and the water already stored in tanks, cisterns and reservoirs.

To protect the constructed spring box and the stream bank, buffer strips will have to be installed. Training the villagers on how to install buffer strips, such as vegetated buffers strips along the streams will ensure protected and improved water quality. The buffers strips are made up of plants and shrubbery that filter and sift sediments, pesticide and nutrients, in addition to other pollutants. They also stabilise the stream banks and prevent destruction of spring box (Mass.Gov).

The community should be taught the importance of regular maintenance of up-ground reservoirs and the water tank maintenance. Compared to steel water tanks, concrete tanks have lower maintenance cost. Educational programs on paint coating are essential. The members of the communities should further be trained on how to conduct formal coating inspections to protect the design life of the reservoirs (VCC.edu). Specifically, those who will carry out the inspection should be trained on how to evaluate the up-ground tanks and structures, paint conditions, structural alignment and leakage of the inflow and outflow pipes. Training should also encompass how to dewater the tank and to eliminate the rusts, blisters and growths, as well as fastening the loose rivets or welding. Further training should be on how to undertake disposal of chlorinated water after tank construction or disinfecting the tank (Uidaho 9-19). It will also prevent corrosion of the iron pipes and dissolving copper and lead from the joints and pipe walls. It will also prevent harbouring and re-growth of opportunistic pathogens, as well as reaction of disinfectants with the organic or inorganic compounds causing odour and taste problems.

Education programs should also be initiated to ensure optimised protection of the walls. The key training programs to the community, specifically those assigned the responsibility of operating the well, should include how to rehabilitate the facility for optimal protection. Training on combinations of methods that can be used includes use of chemicals for dissolving the incrusting particles to allow them to be pumped from the well. Second set of training procedures include cleaning of the well with a brush that is fixed to a drilling rig.

Training on using pressure jets is also vital. The high-pressure jetting, jets water at high pressure to clean the well walls. Additional training includes how to use chemicals to clean the well. Selected chemicals can be put in the wells before being pumped with water to eliminate pathogens. Liquid bacteria acid can be used to eliminate slime and bacteria. Sulfamic acid can be used, alongside the modifiers and inhibitors to eliminate clogs. Chlorine compounds may as well be used to effectively kill bacteria. This will improve water quality, as well as prevent deterioration of the water distribution system (FEMA 26).

Educational programs on harvesting water are essential. In the case of Sandhikhola village, the villagers should be taught how to construct their homes so as to harvest water. Further training should include how to evaluate the cistern for structural alignment, paint conditions and leakages. Training should further cover how to enable special provisions to avoid the first five or ten minutes of rainwater flow, in addition to how to sieve the collected water. This will prevent contamination through cross-connections or from the leaking pipe joints. Additionally, training should encompass how the cistern should be treated after each rainwater collection, using chlorine compound. Overall, an optimal combination of these training programs will prevent cost of replacement, promote hydraulic reliability, as well as improve risk quality (FEMA 26).

Works Cited

Env.Gov. “Guidelines for the Design, Construction and Operation of Water and Sewerage Systems,” 2005. 22 May 2014, <http://www.env.gov.nl.ca/env/waterres/waste/groundwater/guidelines_for_design_constr_oper_wss.pdf>

FEMA. “Water Supply Systems and Evaluation Methods”, 2008. 22 May 2014, <http://www.usfa.fema.gov/downloads/pdf/publications/Water_Supply_Systems_Volume_I.pdf>

Igdata. “Design Brief: Nepal,” 2014. 22 May 2014, <http://lgdata.s3-website-us-east-1.amazonaws.com/docs/380/1053838/B.Design_Brief_Nepal_2014.pdf>

Mass.Gov. “Vegetated Buffer Strips: Slow the Flow to Protect Water Quality,” 2014. 22 May 2014, <http://www.mass.gov/eea/agencies/massdep/water/watersheds/vegetated-buffer-strips-slow-the-flow.html>

Uidaho. “Reservoir Design and Storage Volume” nd. 22 May 2014, <http://www.webpages.uidaho.edu/ce431/Handouts/WA%20DOH%20Water%20Res%20Guidelines.pdf>

VCC.edu. “Water Tank Design and Maintenance,” n.d., 22 May 2014, <http://water.me.vccs.edu/courses/env110/Lesson10_print.htm>

WorldBank. Rural Water Supply. World Bank Office Manila, Manila