Town/City: 

Lima

State/Province: 

Costa

Country: 

Peru

Latitude/Longitude: 

12S 77W

Information supplied by

Kevin Lok

97lokkwk@scar.utoronto.ca

115 Omni Dr., #2305, Scarborough, Ontario, Canada M1P 5B4

 416-296-9118

Dated Sat Nov 27 08:25:54 1999


Information Topics:


City Description:

Lima, the capital city of Peru, was home to over 6.5 million inhabitants as of 1992, some 30% of the total Peruvian population, and accounts for approximately 80% of the national industrial production. Lima is divided into 41 administrative districts and the conurbation extends to the coast to include the port of Callao. The urbanized area of the city is constrained by the Andes mountain chain which runs parallel to the coast and future growth is likely to be along the coastal strip and into three adjacent river valleys: Chillon, Rimac and Lurin. In the past 40 years Lima has grown rapidly, due in part to immigration from other parts of the country. Since 1971 the population is estimated to have doubled from 3.3 million to almost 6.5 million in 1992 (City of the World, 1998). The increase in population has led to increased numbers of people living in non-planned settlements, many of which are not served by water, sanitation or power.

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Climate:

Peru has three different climatic zones: the desert, mountains and the rainforest. But Lima has its own climate, it's generally hot during the summer and grey during the winter when the fog (garua) comes in. It's chilly to cold during these months. Lima is situated just 12 degrees below the equator, but its temperatures, modified by the cold Peru (Humboldt) Current, average 21.0 C in Jan and 15.0 C in July. It has an arid climate with low precipitation; the average annual precipitation is 26 mm; sea mists and occasional light drizzles and fog during the winter supply moisture (Britannica, 1998).

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Basic Hydrogeology:

The Lima aquifer comprises unconsolidated alluvial sediments deposited by the rivers Rimac and Chillon, occurring either as lenticular deposits or as cross-linked beds. The aquifer is of variable width and is bounded by Jurassic and Cretaceous sediments - limestones, marls, arenites, quartzites and mudstones, as well as intrusive granites, granodiorites, diorites and andesites. The aquifer extends from the coastal plains in 'fingers' up to the highest parts of the Rimac and Chillon river valleys. The aquifer is split into two principal formations. The upper part of the alluvial sediments is mainly composed of gravels and other coarse-grained sediments, such as cobble beds, and these reach a thickness of up to 100 m. The coarse-grained sediments have a sand and clay matrix and are interspersed with fine-grained layers, causing variations in the permeability of the aquifer. The primary water-bearing sediment are deposits of old courses of the Rimac and Chillon Rivers, these being coarse-grained and of high permeability. The lower part of the unconsolidated sediments is much finer and is largely composed of sands, silts and mud, which reach depths of up to 150 m. These deposits become increasingly fine-grained with increasing depth, and their permeability decreases. The greater part of the aquifer is unconfined as the material is mostly unconsolidated alluvial deposits, but there are exceptions: e.g. there is a localized confined aquifer in the Callao area where the upper alluvial layers are fine-grained deposits laid down on low-lying land between the Rimac and Chillon (Rojas et al, 1994).

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Water Use:

Besides the fast growing population, the water is mainly used for industrial and agricultural activities. A small portion is for urban uses such as parks and hotels for tourists. Water and sewerage services in the metropolitan Lima are managed by the Lima Water Authority (SEDAPAL), part of the national Potable Water and Sewerage Service (SENAPA) (Binnie and Partners, 1987).

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Groundwater Issues:

There is a substantial increase in demand for water due to the rapid population growth and urbanization in Lima. The result is over-extraction of groundwater. It is not sustainable as the water drops 1-2 m every year (Rojas et al, 1994). The quality of groundwater is the main issue in Lima. The aquifer is heavily contaminated by industrial and domestic faecal pollution as well as the polluted River Rimac that recharges it. The quality deterioration continues up to the point of consumption due to the recontamination in the distribution network (Rojas, 1993). The public health effect of groundwater supply is not only related to quality which requires immediate remedial actions, but also other factors such as continuity of supply, coverage, quantity and accessibility.

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Groundwater Problems:

It is evident that there is significant faecal contamination of Lima aquifer, which represents a risk to public health. A majority of groundwater sources, which supply the distribution network in Lima, are chlorinated to disinfect the water and the goal is to provide a free chlorine residual to prevent recontamination in the distribution network. But recent studies show that only 36.6% of groundwater supplies achieved the goal, the remaining portion did not maintain any free residual due to equipment breakdown, poor maintenance or high chlorine demand and thus do not provide protection against introduction of bacteria in the distribution network. The main sources of faecal contamination of the Lima aquifer are: abandoned dug wells, especially those that are in the industrial sites, that are not sealed; currently used dug wells which do not have a complete sanitary system; inefficient and unlined waste stabilization pond and effluent irrigation at Callao; and the River Rimac that recharges the aquifer, is grossly contaminated with agricultural and industrial pollution with high levels of nitrate and other organic compounds. As in common in developing countries, there is a lack of reliable data, which describe the groundwater quality in Lima that makes groundwater quality assessment difficult (Rojas et al, 1994).

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Solutions:

There is an urgent need for routine groundwater quality monitoring to be established and a thorough hydrogeological survey of the Lima aquifer to be undertaken to establish flow patterns and rates, areas of recharge and increased aquifer vulnerability, the level, type and distribution of existing pollution, and to assess migration rates of common contaminants. In order to improve the groundwater quality, there are a number of immediate actions that could be taken to ensure that the quality of the groundwater supplies for drinking in Lima is improved. The sealing of all unused and unprotected wells in the city with low-permeability material such as clay is a priority to prevent continued contamination of groundwater. This would remove obvious point sources of contamination of groundwater within the city, help to reduce the vulnerability of the aquifer to contamination. Other remedial and preventive measures include lining of the waste stabilization pond to the south of Lima; improvement of effluent quality and modification of irrigation techniques to make them more efficient; control of the quality of domestic sewage and industrial discharges into rivers and near groundwater sources; and introducing restrictions on the use of inorganic fertilizer and pesticides in aquifer recharge area (Bartram, 1990). In order to reduce the pressure on the groundwater supply, Pomacocha-Rio Blanco Water Resource Transfer Project was proposed in 1998. The purpose of the project is to stabilize the volume of water in the Limac River, which falls considerably in the dry period. It also ensures sustainable supply of water to Lima by transferring water resources as a new source of water supply to the Blanco River, a branch of the Rimac River, which flows through Lima, from the Pomacocha Dam (see electronic reference).

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References and Other Author(s):

References/Bibliography: Electronic Reference:


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Contacts:

Local Contacts:
Lima Water Authority
Planta La Atarjea
Km 1 Autopista Ramiro Priale Lima 10
Peru
Tel: 51-1-362-5637
Fax: 51-1-362-3558

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