25 de Mayo, a city on edge due to pollution in the Colorado River

Abstract

Colorado River is the main watercourse of its homonymous basin, located mostly in Northern Patagonia, being at the same time the natural limit between the provinces of Río Negro and La Pampa. Because it has a snow regime, which drains to the Atlantic, it allows the supply of fresh water in sufficient quantities for its various uses and exploitations. This has a particular geographical imprint, given that the resource is capable of providing the supply of drinking water beyond the riverside localities, within an eco-regional and climatic context marked by aridity. However, over the years, economic activities have increased and, with them, urbanizations where a sustainable management of water resources was not implemented.

In this context, upstream of  La Pampa towns there is the discharge of wastewater and the drainage of oil spills or other economic activities, such as mining. For this reason, the city of 25 de Mayo denotes sources of pollution after its almost exponential growth, associated with the hydrocarbon boom that occurred at the end of the last century. Not only were incidents linked to extreme flow oscillations (river floods and droughts) not resolved. Different problems caused by the actions of oil companies and others were also not reversed and, despite its projection, a sewage treatment plant was never built in accordance with the population increase. In fact, this sewage is discharged into the river, believing that the solids settle over after twenty kilometers, until it drains. However, there are previous studies in Casa de Piedra tourist village, beyond the dam, where it has been found that pollution, both from oil spills and sewage discharges, does not disappear downstream. And this affects, among other water uses, the main aqueduct of La Pampa.

Given this problem, the research aimed to verify whether the environmental indicators were persistent towards the year 2023 and, likewise, which alternatives or proposals are more sustainable. To do this, sampling was carried out downstream of 25 de Mayo, in order to compare the environmental situation. This included physical-chemical and bacteriological analyzes of water and arthropods (bioindicators), added to participant observations and interviews with key informants (Delphi System), in order to understand the multicausalities or intervening factors.

After the results in two laboratories, contamination was confirmed in those drains in contact with the river and in the course mentioned. This aggravates the previous situation upstream, mainly derived from the oil hub located in Rincón de los Sauces (Neuquén). At the same time, the dumping of other waste was detected from rural properties and homes located on the riverside strip, installed temporarily or informally. Finally, through consultations with experts in the field and a meeting among the participating team, it was agreed that in addition to requiring a new treatment plant, it is necessary to divert the treated water to forestry or other related uses, which would contribute positively to the productive area, and even to public plantation of trees.