Impact of Human beings on the Natural Environment

Water Usage

Already since the beginnings of Nogales, it was known that the availability of water would determine the future of the town. The Mexican Consul in Tucson reported this in 1882, when he was informing about a new settlement at the border formed by the temporary workers of the railroad, where the Mexican Customs House had been established. He didn't believe that there would be possibilities for it to reach permanency, because of the lack of water, as it was acquired from some wells that had been excavated along the creek.

At the beginning, Both Nogales had it's water supply from local wells, as well as that brought by the railroad to Nogales. By 1898, the Nogales Water Co, who supplied to both towns, discovered an underground source that, the same as today, thought it would be enough for the future development of the towns. A 18" well was excavated where today the OOMAPAS offices (at the Sports Complex) are located. It had a production of 125,000 galls/day, and the corresponding lines, of some 5 miles to distribute it, as well as a 250,000 gals tank were also built.

By March 1899, Dr. W. F. Chenoweth sold Eng. Ignacio Bonillas his part in the water company, so he acquired it's control. However, by 1911, due to the uncertainties of the Mexican Revolution, Nogales, Arizona looked for an independent water supply, and a well was excavated in the Santa Cruz River (near today's bridge over the river, along the Nogales-Patagonia highway), and a distribution tank was erected in the Courthouse hill.

In 1949, Nogales, Sonora, following the example of it's sister city, also built a pumping system from the Santa Cruz River, which brought 3.3 Mmy (million cubic meters a year). And as the population of town grew, the network of wells was also extended. However, the local problems of water supply continued. Among these were the lack of water in the higher areas of town, as well as during the Summers before the rainy season; the contamination by organic contaminants, mainly along the La Granja Creek; as well as the water turbidity during the rainy season.

More recently, in the 1989 Summer, during what was termed as the "most severe crisis... of drinking water that Nogales has suffered in it's history," the Municipal President agreew that Nogales, Arizona would give 400 thousand liters of water a day to Nogales, Sonora, because that Summer not even 150 lt/sec were obtained, for a total demand of 500 lt/sec.

The reason is that the local demand of water in Nogales increases precisely when the river dries out, before the Summer rains, as well as that the wells located along the Santa Cruz River are only shallow, because they are located in a shallow acquifer (See the chapter Hidrology for a better understanding of this), so they dry out soon.

Eight months later, the Sonora State Government announced the investment of 24 thousand million pesos to cover for the deficit (85% of the investment), and also to improve the local sewage network (the remaining 15%).

Five wells were perforated some 10 Miles South of Nogales in the Alisos Watershed, increasing the water supply to 14.2 Mmy, and to 16.1 Mmy by 1991.

There is no International Agreement between the two nations to regulate the international usage of the Santa Cruz River. Nogales, Sonora is currently supplied as shown in the following diagram:

Of the total of water consumption of Nogales, 7.8 Mmy come from the Santa Cruz River, 9.4 Mmy from the Alisos Watershed, and 3.9 from wells located within the city (which are gradually being closed down, as they are contaminated), to reach a total of 21.1 Mmy. However, this water volume isn't enough to cover the current needs of the population.

Nogales, Arizona, uses 8.2 Mmy of water for it's water supply, which is totally taken from the Santa Cruz Watershed.

All of this water (with the exception of that lost through evaporation and leakages), after being used in Ambos Nogales, is purified in the International Wastewater Treatment Plant, located North of Nogales, Arizona and then is reincorporated to the Santa Cruz Watershed. The Plant has a current capacity of 22.4 Mmy.

In Nogales, Sonora, officially 85% of the population is connected to the local water network, although only 39% has water the 24 hours. This is because most of the network is over 30 years old, and therefore needs to be replaced. Also, as the population has increased, the new homes have been just connected to the network, which of course was designed for a much smaller population.

Now, as regards sewage, optimistically it is calculated that 75% of the population is connected to the sewage network. The population that isn't, of course discharges their sewage to the floor, contributing, therefore, to the underground contamination of the Arroyo Los Nogales.

This sewage is filtered by gravity under Both Nogales, and the filtered water also incorporated naturally to the Santa Cruz River.

We should also note that Nogales, Sonora (as shown in the Diagram) is currently using 9.4 Mmy of water from Los Alisos Watershed, which after being used only once in Nogales, is transfered from the Alisos Watershed to the Santa Cruz, and therefore is reused further North, in Arizona, instead of being reused in the Alisos Watershed, from Cibuta to Caborca.

In January, 1996, Nogales, Sonora, received the Certification from the Commission of Border Environmental Cooperation for a water supply and distribution network project, totalling $42 Million Dlls, to be implemented in two phases: Phase I would cover the modernization of the distribution system, while Phase II would deal with the increase of water supply from the Santa Cruz River.

During the Spring of 1996, President Zedillo promised $10 Million Dlls of help to undertake this project.

Finally, more recently, the announcement that $50 million dlls were going to be be used in the production increase of the International Water Treatment Plant.

Contamination

On February 15, 1936, the Mexican Federal Government decreed the establishment of a Forest Protection Zone along the Arroyo Los Nogales. It comprised some 8,650 Has of oak forest, desert prairie and the creek area, although as it wasn't accompanied by a Reglamento, it was ignored and the growth of the city destroyed it, leavint the Decree without implementation.

The fact that Nogales is located along a gully also agravates any kind of contamination by liquids, as these will be contained within the watershed, emigrating downcreek, and also contaminating the subsoil along the Arroyo Los Nogales.

There are two kind of contaminants: Biological, and Chemical.

The first kind, cause mainly digestive sicknesses, while the Chemical contamination can produce cancer, lupus, genetic anormalities, etc.

To prevent the first kind of contamination, it is only needed to inject some kind of organic killing chemistry, like chlorine or any bactericide to kill the microorganisms.

However, the chemical contaminants can only neutralized by "washing" all the undergound soil, or removing it.

There is no doubt that the subsoil along the Arroyo Los Nogales is contaminated. An underground sampling study that was carried out in 1988 revealed that even there, not only the surface waters, but also the sediments located near the Industrial Park, presented a high degree of Arsenic, as well as 1-1 dichloroetane. In another water supply well were also found levels of TCD which were 20% above the standards for drinking water in the US, besides having levels of 1-1-1 trichloroethane (TCEA), as well as 1-1 dicholoroethane close to the maximum permissible level. All of these chemicals were, at that time, used by the assembly plants.

In another study, undertaken by the IBWC, made publid in July, 1988, indicated that in 4 of 7 tested wells along the Arroyo Los Nogales in the Sonoran side of the border, there was biological contamination with coliforms, as well as chemical with Nitrates, Iron, Manganese, and some compounds like tetrachloroetylene, as well a Vinil chloride.

This latest study found contamination even North of Norales, Arizona, in some wells located in Valle Verde, some 5 miles North of the Border.