Stabilisation of the Queretaro Valley Aquifer

Stabilisation of the Queretaro Valley Aquifer

In Querétaro, the main concern on water is overexploitation of aquifers thatsince the fifties have provided water to the inhabitants of this Valley and are alarmingly experiencing high levels of exploitation. Being the only source of supply, solutions must be sought to provide drinking water to all inhabitants of the entity, without compromising the water for future generations.

1. Innovative processes and methodsstabilizing the Aquifer

The metropolitan area of the city of Querétaro was supplied with groundwater onlyuntil 2010 and mainly from the Querétaro Valley Aquifer. With the addition of 1.500 l.p.s. of surface water from theAqueduct SystemII, the way we operate the wells has changed, starting with an operational strategy to replace groundwater volumes for surface water. The extraction of the Querétaro Valley Aquifer is estimated at 110 million m3/year, which has caused a strong mining of the aquifer since the total recharge is around 70 million m3/year, resulting in the overexploitation of groundwater.

This imbalance between the difference of recharge and extraction with a deficit of 40 million m3/yearhas brought consequences in the area:

• Collapse and subsidence of the land, causing some faults and fractures that threaten the stability of urban areas in the city, which has a greater exploitation.
• Increased groundwaterpumpingcosts, due to a lowering of the levels at a rate of 2.9 m3/year.
• Decreased life and performance of the wells.
• Deterioration of water quality in some areas of the aquifer, sinceextraction levels are deeper.

Exchange of 1.500 l.p.s. of surface water of the Aqueduct System II for groundwater

In order to satisfy the constant drinking water demandfrom the growing population of the state capital and stabilise the Queretaro Valley Aquifer, the State Water Commission has carried out the search, identification and evaluation of projects and supply sources to meet these demands.

One such project is the Aqueduct System II, which began operations on 17 February this year, adding a volume of 47 millionm3 (1.500 l.p.s.) annual of surface water for the inhabitants of the metropolitan area of the city of Queretaro, the investment for the system was MXP$2,854,373,202, includingBANOBRAS FINFRA programmecontribution of non-recoverableMXP$800.4 million and the supplement was obtained through the private sector with the BOT scheme, which is used in infrastructure in developed countries and allows to carry out high-priority projects for a society without having to absorb the investment at the time of its execution.

On April 6, 2011, the Alcanfores IIwell was closed, which marks the beginning of volume reduction of groundwater extraction in the Querétaro Valley Aquifer.

Currently the wells operation was reduced from 24 to approximately 11 hours a day to reduce the extraction volumes of the Queretaro Valley aquifer of 47 millionm3a year.

In regard to volumes produced for February to May 2011 (15.36 million m3) the extraction in the Querétaro Valley Aquifer has decreased to 9.4 million m3, compared to the monthly average volume for the same period in 2010 (24.76 million m3).

The second action that is being carried out for the benefit of the Querétaro Valley Aquifer is the reduction of demand through flow recovery in the distribution system.

The water lost in the network represents a high cost to the state of Queretaro, for the investment in major projects to bring it from long distances, as well as extracting and purifying groundwater before delivering into the network.

Flow recovery is an important point to reduce leakageincidence, which is performed by replacing networks in poor condition. Currently, 36% of the network has more than 25 years and/or is in a critical condition, 20 colonies of the city have been identified that represent almost 50% of total leaks in the network.

To decrease onleaks incidence during 2011-2015 it is planned to invest 1,100 million pesos for the replacement of 765 km of network and an estimated recovery of 395 l.p.s., these actions will increase the physical efficiency of the drinking waternetwork, reduce leaks and stop extracting this volume from the Queretaro Valley Aquifer.

The third action is rainwater induced infiltration with absorption wells into the unsaturated Querétaro Valleysubsoil

Sites were selected for theabsorption wells taking into account the geo-hydrological characteristics and conditionsof the subsurface, which favour water infiltration and movement in the unsaturated layers of the aquifer, obtaining the rainfall volume that the sub-basinsprovide.

This project involves the following institutions: CONACYT (National Council of Science and Technology), CONCYTEQ (National Council of Science and Technology of the State of Querétaro), CIDETEQ (Centre for Research and Technology Development in Electrochemistry of the State of Querétaro), Water State Commission of Queretaro, Institute of Geosciences, UNAM (National Autonomous University of Mexico) and the Faculty of Engineering UAQ (Autonomous University of Queretaro).

To date we have drilled four wells, three for absorption in: Ciudad del Sol, Corregidora Stadium and UAQ Sports Complex, and one under study, La Gloria, for rainwater infiltration into the unsaturated Valley of Querétaro subsoil.

La GloriaWell is completed at 150.00 metres depth and under implementation process with: Diver to monitor the static level, tensometers to monitor vertical displacements and piezometers to monitor water intakes at 20 and 140 metres deep.

The Corregidora StadiumWell is completed at 100 m depth and tests were made to the filling absorption flow, using a volume of36 m3, at a filling time of 9.0 minutes and 100 to 50 mdepth.

The UAQSports Unit Well is completed in full and tests were made to the filling absorption flow, using 36 m3volume, at a filling time of 9.0 minutes and 100 to 50 mdepth.

The Ciudad del SolWell, is completed at 80.00 m. with an absorption rate of 16.66 l.p.s. and it is expected, based on the trend curve projection, to reach 100.0 m, with anabsorption flow of 25.64 l.p.s.

Also, the depth of these three wells is up to 100.0 m and not reaching the 140.0 m ± depth ofthe static level of the Queretaro Valley Aquifer.

Finally, the stormwater infrastructureprojectsare completed and under review.

This action not only pursues the primary objective of infiltrating water in the aquifer, but also aims to manage the flooding problem in the urban area of Queretaro, contributing to control surface runoff volumes.

The fourth action is the Moctezuma and Santa Maria River surface water reservoir to supply water to the inhabitants of the State of Querétaro.

There is a Water Supply Plan for the State of Querétaro forsurface water future demand and availability of watersheds in the Moctezuma, Santa Maria and Extoraz Rivers of the Panuco 26 Hydrologic Region.

CONAGUA published on 2 July 2009in the Official Gazette, the AGREEMENTstating the results of technical studies of national surface water in the mentioned above hydrologic region watersheds.

Water volumes to be reserved

CONAGUA prepared the document on the water volumes to be reserved to send them to the Federal Official Journal for publication.

The study’sresults of316 million m3 of surface water availability in the 26 Panuco hydrologic, make it feasible to supply the national surface water reserves in the Santa Maria and Moctezuma rivers watershedsand thereby ensurewater supply for the population until 2105, i.e., for the next 100 years in the State of Queretaro, as well as its socioeconomic development.

The fifth action is treated wastewater reuse and water culture.

It should be emphasised that due to its importance, actions have been taken to promote the reuse of treated water in landscape irrigation, agriculture, industry and in some neighbourhoods of the city; in all cases, where the replacement of drinking water for treated wastewateris possible.This allows us to free volumes from the aquifer to prevent its overexploitation. Actually, 16.27 million m3are being reused per year in the metropolitan area of the city of Queretaro.

Developing a broad and updatedculture on the rational use of water is one of the State Water Commissionactivities, an on-goingmission through the school programme in preschool, primary and junior high school education, the community programme and events such as the World Water Day, State Competition Children's drawing and painting, in 2010 these events were held for the benefit of 74.455 inhabitants.

Impact on the Queretaro Valley Aquifer

The geohydrological balance of the aquifer would reach a steady trend in its recharge-extraction ratio and a gradual decrease in the abatement rate of aquifer levels that are currently of 2.9 m. per year.

This will stop the progress of subsidence in the affected areas of the city due to overexploitation of the aquifer, preventing deterioration.

According to the numerical model of groundwater flow dynamics, abatement levels are estimated to be reduced between 0.8 m. and 1.0 m. a year

Consider groundwater as a strategic reserve to supply future generations of the metropolitan area of the city of Queretaro.

1. innovation processOriginality

This project is considered innovative as it is not known that there is in Mexico or Latin America anaquifer stabilisation project and considersgroundwater as strategic reserves for future generations.

The actions being undertaken in a comprehensive manner to stabilise the aquifer are:

• Exchange of 1.500 l.p.s. of surface water from the Aqueduct System II for groundwater.
• Flow recovery through massive network replacement of 765 km and estimated recovery of 395 l.p.s.
• Induced rainwater infiltration through absorption pits in the unsaturated subsoil of the QueretaroValley.
• Surface water reservoir of the Moctezuma and Santa Maria Rivers for water supply in the State of Queretaro.
• Treated wastewaters reuseand water culture.

This project represents a very important experience, being the basis and model for the recovery and stabilisation of the Querétaro Valley Aquifer and encouraging more organisations and States to replicate it in other aquifers.

Feasibility of replicating results in other utilities

Overexploitationis the resultof excessive waterextraction, ever-increasing demand for agricultural, urban and industrial use, resulting in the abatement ofwater levelsin the aquifer andquality deterioration and destructive exploitation thereof, which is difficult to recover.

The information and experience generated in CEA Queretaro concerning the stabilisation of the Queretaro Valley Aquifer willset the technical basis that supports actions and policies for the development and rational use of water in other cities and states.

Most of Mexico's urban population depend on groundwater, it is important to consider the experiences in the recharge of aquifers and stabilisation to reduce abatement in water levels and contribute to a better and rational use.

1. Impact of the process or technology in environmentalcare and rational use of water.

The most evident impacts of aquifers overexploitation are the major subsidence of soil and sub soil, as groundwater is extracted the gaps formed are not filled again by water causes a rearrangement of land and subsidence that substantiallydamaged urban structures, apart from making them more susceptible to geological risks.

Expected results are directly related to the stabilisation of the Queretaro Valley Aquifer byceasing to extract the volumes supplied by the Aqueduct System II and flowrecovery, reducinggroundwaterexploitation, additionally to the artificial recharge to be implemented, thus meeting an ecological problem and its remediation.

In the State of Queretaro actions are been taken for a better watermanagement, optimisation and efficient use.

For a society with a greater commitment awareness on environmental stewardship and rationalwateruse

1. Population served and/or number of intakes by utility.

Currently the system for the metropolitan area of the city of Queretaro is supplied with 212,140 drinking water intakes benefiting 958,327 inhabitants, with one of the highest growth rates in the country.

The State Water Commission of Queretaro seeks to reverse the adverse trends of resources and lay the groundwork for Querétaro to be a state with sustainabilityin drinking watersupply, using more effectively the available volumes of surface water and groundwater, requiring and promoting joint participation of the authorities, users and society in general in the efficient use of water, protection of water bodies and preserving the environment for future generations.

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