From the origins of human communities, the first waterworks responded, in most cases, to evident and immediate needs of the population and its economy. They were therefore small projects for satisfaction of drink and hygiene, irrigation, energy, navigation, flood attenuation, conceived and exploited in many cases independently from one another. In that context, water demand was very low compared to the supply. Water was a natural gift, a renewable resource of infinite availability and, therefore, human populations assumed that it should be free (Capurro et al, in preparation). The growth of demand (due to increase in number of users and units of consumption) determined the increase of size of such waterworks, the consequent appearance of interference and interaction with the hydrological cycle -scarcity- and a competition between sectors of users.
In addition, the quality of both superficial and underground water resources started to deteriorate, as a consequence of human activity, especially in big urban concentrations. Many watercourses were not fit for any type of usage, generating infested and degraded areas in the surroundings. The response to these processes was a change in the conception of water as a natural gift, a limitless renewable resource. Water has ceased being an entirely renewable resource (its supply has decreased in time).
From the 1,400 million cubic kilometers of water in the world, only 1% is in the hydrologic cycle, of which half is in lakes, and rivers. Even so, there is more than enough water to cover current and future demand. The problem is that it tends not to be where it is needed, or it is of poor quality.
The amount of water used at the community level depends on various factors. Among them, we find climate (more water is needed in arid areas compared to humid areas), and socio-economic levels of the population. But mainly, water demand depends on its availability. People adapt to available volumes of water, so it could be stated that the greater the volume supplied, the greater its consumption level. Another important factor that affects water demand is existing service infrastructure, i.e. piping systems, treatment, storage and distribution. The policies implemented by the authorities can also be used to regulate water use. Those related to consumption records and prices are probably those that affect demand the most. Finally, the efficiency of technology to extract and use water can affect its demand. Better technologies would allow a greater availability of water, both for urban and agricultural use (Capurro et al, in preparation).
One of the most important problems in designing water strategies is related to water assignment policies and establishing priorities for different uses. The most common policy of price fixation is a canon mainly conceived to recover costs. This type of uniform price is not fixed as a function of the volume used, and is widely criticized because it lacks incentives to control water usage.
An important cost of water supply relates to its conduction from the place of production to place of consumption. Consequently, the nearer a water source is to a city, the more attractive it will be as exploitable resource. Generally, urban users can pay much more for each unit of water volume because transportation costs are divided among individuals and companies.
The hydrological sector constitutes a system depending on activities and processes, among them are agriculture and fishing, energy, industry, transportation, population dynamics, ecosystem preservation, recreation. As such, its integrated planning must take into account the available previsions of the development of these activities and processes. Uncertainties in determining these changes in development will affect the quality and even the validity of planning strategies.
In Argentina, the policies for water management were created as a response to regional growth and to problems that appeared during its development. The nation first, and the provinces later, followed this process and this is how currently there is a great disparity of criteria along the country. In many provinces, there is no water legislation that accounts for an integrated approach to this issue. Nevertheless, different institutions were created that coordinate, administer and regulate the development and management of water resources. With respect to a price for water, no policy has been applied to encourage its efficient use. The value of the canon is generally insignificant and fixed by political criteria more than by economic efficiency. In many cases, it is counterproductive in the sense that it provides free access to agriculturists inexperienced in irrigation systems, leading to elevation of groundwater table and salinization (Capurro et al, in preparation).
The use of water for agricultural use in Argentina depends on the provinces, which have the political right to manage their natural resources. The pampas region in Argentina, which concentrates most of the country's population, industrial activity and agricultural activity, is a great demanding area of water. An increase in demand is expected, not only due to urban growth or industrial activity, but also due to the important appearance of irrigation. For this reason, it is necessary to define water management strategies considering all the elements in the water equation.
The purpose of this study is to propose policies that allow for equitable water allocation between competing activities in the Reconquista River Basin, located in the Province of Buenos Aires (Argentina). This area expands to the northwest of the greatest metropolitan area of Argentina, the Metropolitan Area of Buenos Aires (MABA). The waterhead of this basin is located in a predominantly agricultural and agro-industrial area. Towards the river's mouth, urban and industrial density increases, as well as its pollution levels. Most of the basin lacks sanitation infrastructure, and the main water supply are the underground aquifers and water tables nearer the surface, in some cases contaminated with fecal bacteria and industrial pollutants.
To accomplish this objective, it is necessary to understand the underlying interaction of population in environment, in terms of different types of transitions and their stabilization. The information used was: