Sustainable engineering practice and implementation

Sustainable Engineering Practice

Water is an essential, replenishable resource. Water resources require conservation regardless of whether a country has high or low rainfall. Regional autonomy and varying local conditions also call for local specientic plans and approaches to water resource conservation and utilization.

As water becomes an increasingly scarce resource, a future trend must be towards more and better utilization of water, in particular rainwater, in urban systems. Rainwater is a discarded resource, and its mismanagement can result in major environmental problems and disruptions such as urban run-off. 41 But there are simple technologies available that local governments can introduce, which can save rainwater for drinking and other purposes. The big dam age is, by and large, unfinished, with only a few dams in the world really having lived up to initial expectations. Rather, alternative approaches are needed, such as smaller cascading dam engineering and applications of underground dam technologies.

Cities are great consumers, and water is no exception. They require large amounts of water to sustain themselves, owing to the sheer numbers and density of housing. To meet their demands, there has been a variety of ways in which cities have accessed water and managed needs. The most typical pattern to date has been to build a large dam or central water supply and pipe in the water as needed. This type of exercise can be ecologically disruptive, as well as costly. One of the resources that maintains potential for exploitation is rainwater, as a renewable natural resource to which we generally have access. Usually cities have access to rainfall, which opens up possibilities for its improved application and for innovative water management methods. Generally, the larger a town or city, the more difficult it is to achieve sustainable water resources and to maintain regional water circulation. The following three scenarios illustrate problems which exist worldwide:

Scenario 1: Groundwater is available in adequate quantities and of good quality, but the demand for potable water continues to rise with the growth of the town, while the new formation rate for groundwater is reduced because rainwater can no longer seep into the subsoil naturally. More roads, paths, paved areas, dwellings, public buildings, and industrial plants work to seal the surface, and the town comes to "import" potable water from other regions, which endangers nature through heavy extraction of water and dependency on this region. Another problem concerns the quantity of rainwater flowing off the surface, which rises dramatically when the surface is sealed. This causes flood damage and rising costs for sewers and the cleaning of wastewater.

Scenario 2: Potable water is obtained from surface water, a river or lake. The treatment for making potable water is technically expensive because other communities lead their poorly cleaned wastewater into these open waters. As a result of this exercise, potable water becomes extremely expensive; so expensive that large sections of the population can no longer afford it. As a consequence, social unrest can then be avoided only by subsidies. The town is socially and entinancially heavily burdened. Another problem is that the spontaneous rainwater flow, mixed with wastewater in a heavy downpour, pollutes the river or lake once again and provides more problems for gaining potable water.

Scenario 3: As a result of climatic and geological conditions there is little potable water available; the resources are quickly exhausted. The possibilities for development by the town are therefore restricted. The cost of a long-distance water supply is prohibitive.

This paper examines possible applications of rainwater utilization and application in an urban context. In doing so, it examines some of the more available technologies for this purpose, and draws on Germany's experience in dealing with the related issues. As part of this discussion, variants of practice and boundary conditions of decentralization issues are raised.

Questions and demands

Centralized water systems have come up against various problems before. They are expensive, ecologically and socially disruptive, and can drain whole communities of entinancial and other resources. One of the ways in which water utilization and management is being considered recently is in terms of decentralization of functions. Decentralization of water services is coming to be seen as a preferable alternative to the previous types of centralized system. However, there are questions that need to be examined. Can decentralized measures be realized in towns too? What measures are especially suitable for towns? How can partnerships and collaborations among cities and transnational networks help to solve these problems?