Early in the 20th century, Monterrey, Mexico began a successful economic metamorphosis and growth pattern that remains an exception in Mexico. This all began with increased investments in irrigation that fueled a boom in agriculture and ranching for this northern Mexican city. The economic growth has fueled income disparity for the 3.86 million residents who live in the Monterrey Metro area (MMA). In addition, the rapid urbanization has taken a large toll on the water resources. In addressing many of this challenges, the city of Monterrey has become a model for sound and effective Integrated urban water management.

The challenges that Monterrey has confronted pertain to scarcity of surface water resources, poor water quality due to untreated industrial effluents, political cycles and term-limits which can limit long-term vision, and water disputes between urban and agricultural users. Monterrey has good groundwater "well-fields" that supply about 40% of the water demand for the city and generally are not over-exploited because of good connections to high-yield aquifer systems in the central parts of the "Curvatura de Monterrey". These wells are managed as storage reserves that can be used in time of drought, which is quite common in this region of Mexico.

Also unique to Monterrey is an arrangement made between farmers and the municipality, whereby the farmers grant the use of their water rights from the nearby Cuchillo reservoir and the municipal water utility SADM (Servicios de Agua y Drenaje de Monterrey) returns urban used and treated water to farmers for irrigation. This arrangement has benefited both parties since SADM supplements its water supply with high quality but internmitent supply from the Cuchillo reservoir and farmers receive a consistent and full of nutrients water for irrigation. The longer term outlook for the area is for urbanization to continue and water availability to decrease, therefore, new water management strategies will have to be created.

Economic and social During the first half of the 1900s, high investments in irrigation infrastructure had spurred agricultural development.

Referred to as the "Mexican miracle" from the 1940s through the 1970s, rapid economic and population growth transformed Monterrey into the second most important industrial city and second largest city in the country with a metropolitan population of 3.8 million. Monterrey's rapid urbanization was driven in part by the development of assembly plants (‘‘maquiladoras’’) and expanded significantly with the 1994 signing of the North American Free Trade Agreement (NAFTA). More specifically, the electronics industry became the largest industry in Monterrey and employs large volumes of industrial solvents in its productive process. These harmful chemicals are the most serious concern to surface and ground water in the Monterrey metro area §k§l§6Hola=D.

A water shortage in the late 1970s forced rationing on 750,000 people, most of whom were poor and already experienced low access to water. Forced water rationing spawned water protests that escalated to larger organized mass rallies, blockades, seizure of water service trucks, taking over of government buildings, and the holding hostage of water delivery drivers. Most of these actions were led by poor women and resulted in presidential action with the creation of the "Water for Everyone" (Agua para Todos) program that ushered in a new era of government spending that promised to bring water to every resident by 1985.

Geography and climate Monterrey is the capital city of the state of Nuevo León, and is situated approximately in the center of the state located in NE-Mexico and close to the Texas border. Monterrey has an elevation of above sea level and is located in a wide basin about across, surrounded to the north, west, and south by mountains. It has a semi-arid climate with a mean temperature of 75 °F (24 °C). However, most of the year temperatures are either warmer than 82 °F (28 °C), or cooler than 57 °F (14 °C). Monterrey's annual rainfall averages 584 mm (23 inches), with most of this total falling between June and October during the Atlantic hurricane season.

Water availability In 1995 the population of the San Juan watershed was 5m inhabitants, of which approximately 4m were in Metro Monterrey (MAM) and the population is expected to increase to 8.4m inhabitants by 2020. The population of MAM is located within 360 km2 across nine municipalities (Apodaca, Garcia, Escobedo, Guadalupe, Juarez, Monterrey, San Nicolas, Santa Catarina and San Pedro). Taking discharge and aquifer recharge, current population and average hydrology into account, the watershed possesses a water availability of 484 m3 per inhabitant per year and would be reduced to 230 m3 per inhabitant per year by the year 2020. The watershed therefore ranks amongst the poorest regions in regards to per capita water availability with countries such as Syria, Israel, and Saudi Arabia. Per capita water use estimates, including domestic, commercial, municipal, and industrial supplies, approach 290 liters per day per inhabitant for MAM. More specifically, the MAM receives 60% of their water supply from surface water while the remaining 40% comes from an extensive network of groundwater wells.

Surface water: The San Juan River with a surface area of 20,212 km2, accounts for 31.5% of the entire surface area of the State of Nuevo León and is the largest and most important river in supplying water to Monterrey.

Storage Reservoirs: El Cuchillo dam (1,123,000,000 m3 active capacity) was constructed 75 km upstream of the Gómez dam and began operations in 1993 primarily to supply water to Monterrey. The Marte R. Gómez (MRG) dam, constructed in 1936 just upstream of the San Juan's confluence with the Río Bravo, serves as the Bajo Río San Juan (BRSJ) irrigation district's principal reservoir with 829,900,000 m3 active storage capacity. The José López Portillo ‘Cerro Prieto’, reservoir (ordinary storage capacity 393 mm3) was built in the early 1980s in the adjacent Rio San Fernando watershed to supply the domestic and industrial water demands of Monterrey Metro Area (MAM), and was the first case of inter-basin transfer of freshwater to cope with shortages in Mexico's northeast.

Groundwater: Monterrey groundwater is accounted for by 46 deep wells (700 to 1000 m), 74 wells (<100 m), three water tunnels (Cola de Caballo I and II, San Francisco), and two major springs. The wells are located in the ‘wellfields’ (area with many boreholes) and contribute 40% of the total water that consumed in Monterrey. The three most important ‘wellfields" are the "Metropolitan Area of Monterey Wellfield", "Buenos Aires Wellfield", and "Mina Wellfield". The "Buenos Aires Wellfield" is the most important and contributes nearly half (46%) of the groundwater extracted (~ 1.5 m3/s). It is located in a mountainous area of the "Huasteca Canyon" close to Monterrey. These ‘wellfields’ provide high quality water with a low cost of treatment.

According to data gathered by researchers at the Autonomous University of Nuevo León in Mexico, a medium annual precipitation of 538 mm/year within the Buenos Aires wellfield's catchment area is sufficient to recharge the aquifer while allowing for a discharge of around 1,600 L/s (400 gal.) that can safely be extracted at any given time. In 1998, the wellfield was operated at a mean discharge of 1,535 L/s. Due to higher extraction during most of the last 25 years however, dynamic levels in some of the wells have been observed to drop almost 100 meters over a period of several years indicating possible over-exploitation. While this does occur, the wellfields are quickly and completely recharged back to artesian conditions by hurricanes that have passed through in recent decades. Hurricanes do not appear in the hydrological balance that is based on 538 mm mean annual precipitation, therefore, long term aquifer reserves are considered to be significantly higher, implicating that extraction from the Buenos Aires wellfield can be considerably higher than 1,600 L/s without overexploiting the aquifer system.

Other sources of water include man-made tunnels and natural springs (3.20% of total supply); water culture programs, reusable water from wastewater treatment plants and rehabilitation of groundwater wells that now provide access to aquifers.

Infrastructure

Drainage Management of drainage infrastructure is the domain of SADM. Despite comparably low rainfall, Monterrey receives storms and hurricanes of great intensity during the months of May and July. Drainage has been under relative control during these storms. Flooding from storms is also a distinct possibility during September and October, therefore the government has sought to protect the citizens of Monterrey by building 160 km of drainage infrastructures including: 1) seven large storm water canals totaling 60 km; 2) three retention dams; 3) 47 smaller drainage branches totaling 70 km; 4) and 26 km of other municipal works.

Irrigation The irrigation districts within the watersheds serving the MMA are the Bajo Río San Juan (BRSJ) irrigation district #26 (ID026) and the Bajo Río Bravo (BRB) irrigation district #25 (ID025). The farmers in these two irrigation districts receive water through a unique compensation arrangement that includes crop loss payments on the order of US$100 per hectare un-irrigable land due to the diversion of water to Monterrey plus an additional 60% of the diverted water to be returned to farmers as treated effluent via the Ayancual Creek, Pesquería River. While this has been a success, the Mexican irrigation sector will continue to face intense competition for water given: (a) low water productivity in agriculture leading decision-makers to allocate water to higher productivity uses particularly in cities; (b) priority accorded to the domestic use component of municipal water supply; (c) and Mexico's national interests in meeting its water sharing obligations with the United States.

In 1992, when the National Water Law (Ley de Aguas Nacionales) was enacted, management of water and irrigation systems became decentralized from the federal level to state and municipal levels. Irrigation districts, from that year on, became open to privatization and have since been responsible for maintaining themselves. Immediately, the lack of federal funding and resources to the irrigation districts around Monterrey caused problems such as lack of maintenance and management capacity. As the MMA continues to urbanize and demand for water supplies grow for both industrial and public use, irrigation districts 025 and 026 are seeing their irrigated lands contract.

Water use and coverage Water from the Río Bravo including the San Juan sub-basin are used as follows: 78% for agriculture, 12% for urban-public supply, 8% for industry, and 2% for Livestock. Monterrey has 99% coverage in water supply and 98% in sewer and close to 100% in wastewater treatment. Despite high coverage and efficiency rates, the city continues investing in expanding its capacity and improving its operations. Recent statistics show mean domestic water consumption for the city at about 12% of total discharge (Mexico average = 17%) or 10,400 liter per second (~2750 gallons) with lows in winter of 9,300 L/s (2,457 gallons) and high peaks in summer of 12,100 L/s (~3200 gallons). SADM estimated 2002 daily per capita domestic water consumption to be 130 L (32.5 gal.), down 18% from 1997 due to constant supply of 335 million m3/year even though there has been a constant increase in population.

Water challenges

Pollution