Used Water Tanker Trucks

In some countries, water is routinely transported from regions where it is plentiful to regions where it is scarce. Several water conveyance and distribution techniques are available, and are actively used in many countries of Latin America and the Caribbean.

Technical Description

Among the most common water conveyance methods are tanker trucks, rural aqueducts, and pipelines. In some cases, this involves the transfer of water from one portion of a river basin to another, or between river basins. Each of these methods is described below.

· Tanker Trucks

Tanker trucks are fitted with a cistern or storage tank to transport and distribute water from a point of supply to the point of use, particularly to suburban and rural areas not served by a piped supply. If water is not supplied from a central treatment facility, it is usually extracted from the closest natural source (rivers, canals, reservoirs, or groundwater sources) and transported by the trucks to the point of use. Water thus transported may be pumped into a storage cistern, dispensed directly into household or other containers, or discharged into a small-scale treatment facility for centralized distribution. The tanks on the trucks are usually manufactured locally, and some trucks are equipped to carry portable pumps to extract the water from its source.

· Pipelines

Water may conveyed through pipelines by gravity flow or by pumping. The latter system will be significantly more expensive to construct, operate and maintain than similar gravity-flow systems. Large-diameter pipelines can be used to convey water over large distances, while smaller-diameter pipelines can be used to provide bulk or individual supplies at the point of use.

· Aqueducts

Aqueducts are canals used to bring water from a river or reservoir to a water distribution center. The main factors to be considered in the design of an aqueduct are the demand to be met, the source of the water, the topography in the area in which the aqueduct is to be built, the size and nature of the storage facilities, and the size and location of the distribution network. Aqueducts are best suited to meeting large-scale demands in areas with a fairly flat or gently sloping landscape suitable for conveying water to the point of use by gravity.

Extent of Use

Tanker trucks are used in most rural and urban areas of Latin American countries and in some Caribbean islands. Most trucks are privately owned; in some cases government sells the water to truck owners who then resell it to users.

Rural aqueducts have been built throughout the region and have been used to supply water for agriculture and domestic use in rural areas. Interbasin transfers using pipelines are common throughout the Latin American region.

Operation and Maintenance

Pipelines and aqueducts, whether operated by gravity or by a pumping system, need regular maintenance and repair of the pumps, pipes, and canals, and periodic upgrading of the facilities. Problems with water leaks, pumps, and storage facilities require immediate attention in order to avoid interruption of services.

Maintenance of the distribution system includes servicing the pumps and other treatment plant components, inspecting the diversion systems and pipelines, repairing leaks, and replacing electrical motors and other moving parts. A number of problems were encountered in the operation and maintenance of a distribution system in Jamaica.

The level of skill needed to operate these systems is medium to high, and involves some technical training of the operators.

Level of Involvement

In Jamaica, water distribution projects using pipelines have had a high level of government participation. The projects were conceived and designed by the government, funded by an international agency, and constructed by a group of engineering consultants, with overall project coordination provided by government. Easements to permit the pipelines to traverse private property were purchased by the government.

Costs

The costs of these conveyance systems vary depending on their capacity and complexity, as a function of the terrain, the availability of labor, and the demand to be met. For example, in Panama, a small aqueduct system designed to serve a few families cost $500. In Jamaica, the cost of gravity and pumped-source pipeline conveyance system is shown in Table 3.

Table 3 Cost of a Pipeline Water Transfer System

Operation and maintenance costs are a function of the specific problems that can affect each project, such as clogging of intake pipes, or high turbidity and/or high values of coliform bacterial in the source water that requires treatment prior to use.

Effectiveness of the Technology

This group of technologies spans a number of scales of application. Tanker trucks are an extremely effective means of distributing potable water to urban and rural populations, especially as an emergency measure. Their use on a day-to-day basis is more costly in the long term than providing a piped supply, but, again, the method provides an effective short-term solution to a water supply problem. On a larger scale, use of aqueducts and pipelines can provide bulk water to users at a competitive cost. While these latter technologies are limited by the cost of operation to less-steep terrain, they are widespread throughout Latin America and the Caribbean. By varying the diameter of the pipes (and, to a lesser extent, the geometry of the channels), these technologies can span the range of requirements from large-scale source-to-treatment-works applications to individual user delivery applications.

Suitability

This technology is suitable for use in areas where piped water service is not available or has been interrupted. The use of aqueducts is well-suited to transporting large volumes of water over great distances. They are usually associated with impoundments, and are most often used in arid and semi-arid areas.

Advantages

Tanker trucks:

Pipeline and aqueduct systems:

· Electricity can be generated along the pipeline route if there is significant head and flow.

· Industrial and agro-industrial enterprises can be situated where water is otherwise unavailable if economic factors are favorable.