Securing a Future With Water Along Peru's Rimac River Valley

| 20th July 2017
San Mateo's dam sits slightly under half full, while farmer's collective members and Aldo Cardenas, of The Nature Conservancy discuss future plans

Along the Rimac River Valley of Peru, local farmers have taken the problem of water security into their own hands and embarked on a combined reforestation and water storage project, which not only provides safe water but has empowered the local community and, thanks to improving the mountainside soil stability, has reduced the risk of devastating landslides. FOREST RAY reports
One of the largest and longest running disputes involving the Rimac's water is how to curtail and clean mining-related pollution

Alejandro Cordova stands upon a lush green patch of land on a nameless peak in a region called Cancha Moya - just a few minutes' drive up a narrow and bumpy dirt road from San Mateo, in Peru's Rimac River Valley. He holds a handful of a long native grass that looks a bit like rye grass in his hands and rubs it between his fingers.

"These plants are going to save humanity," he says.

It's a big claim and a hard one to defend, but actually, he's right - the grass in Alejandro's hand and others like it may very well save dozens of communities living along the Rimac River.

Alejandro stands alongside several members of the local farmers' collective and Aldo Cardenas, who heads The Nature Conservancy's Lima office and its Peruvian water projects initiative, Aquafondo. Three years ago, the farmers' collective approached The Nature Conservancy (TNC) with a proposal to develop a plot of land belonging to the community as a water fund site. Here, reforestation techniques would be employed to restore a degraded mountainside and provide a useable water source for cultivation, cattle and human consumption. Three years on, the project's success is encouraging other water fund projects and providing a template for how stressed water sources can be managed along the Rimac River and beyond.

Increasing Demands on the Rimac

As stressed resources go, the Rimac River easily makes the list. Lima's roughly 9.5 million residents, as well as the estimated 81,000 people living upstream depend upon it for drinking water, power and sewage services. Commercially, the river's water is also used for mining, farming, bottled water production and hydroelectricity, which accounted for approximately 48% of Peru's total energy in 2015.

But the strain placed by mining companies and a decline in seasonal precipitation, have drastically reduced the river's flow. In fact, the Rimac no longer reaches the ocean during the months of November and December. To maintain a steady flow to Lima's population, Sedapal, Lima's water management authority, has developed a series of dams and connected lagoons in the mountains east of Lima and a system of smaller reserve tanks throughout the city.

Sedapal's mountain reserve system has a capacity of 310 million cubic meters (MCM) - equivalent to 124,000 Olympic-sized swimming pools. Despite such capacity, estimates place Lima's annual water usage at 700MCM. Assuming the rains were to fail one year and the reservoirs were full, which is rarely the case, Lima would have less than a six month supply of water.

Compared to other dry cities, such as Santiago, Chile, Lima's per capita water use is quite high, at around 250 liters. These high usage rates stem from Sedapal's past success in ensuring water access to residents. As Dr Fiorella Miñan, of Care Peru, points out, Lima's residents have never felt the effects of a drying climate firsthand. That all changed during the recent extreme weather phenomenon dubbed the Coastal el Niño, which triggered weeks of unprecedented rains in lands that used to be bone dry.

One of the largest and longest running disputes involving the Rimac's water is how to curtail and clean mining-related pollution

The heavy rains brought on by this weather phenomenon caused widespread flooding and landslides, several of which combined to shut down Lima's treatment plant for several days with more than 300,000 metric tons of accumulated dirt and rocks. Water services were disrupted throughout the city, including, for the first time, Lima's wealthier districts. This prompted days of chaos, with bottled water prices soaring in supermarkets, and long queues of residents waiting for municipal water trucks to fill buckets in the heat.

"I'd never seen anything like it," says Aldo Cardenas, of TNC. "You couldn't find bottles of water in a single store."

Progress in San Mateo

While Sedapal grapples with big projects like a desalination plant, aimed at delivering portable water to its millions, smaller projects that can mitigate the occurrence of landslides, like that at San Mateo are no less vital.

Now in its third year, the farmers, with help and financing from TNC, the Backus Foundation and the Fondo de las Americas (FONDAM), have built a small reservoir capable of storing 300m3 of water and installed a series of dykes that slow the downward flow of water. They have planted pine trees throughout the site, both as an added soil stabilizer and to provide the farmers with firewood from the trees' branches. A lagoon lies on the highest ridge overlooking the site, which the collective and their partners plan to dam soon, thereby providing them with an even greater alternate source of water for agriculture and consumption.

Raúl Zegarra Isla, one of the collective's members, takes twice-weekly soil samples above and below the dykes to measure their efficacy in retaining water. Although this year's uncharacteristic rainfall has complicated these measurements, Zegarra says that the San Mateo site retains significantly more water than a neighbouring site called El Testigo, which does not have a dyke system.

The most prominent plants in the area are grasses. Alejandro explains that these grasses are vital to reforestation; they grow better at high altitudes than many other plants and create a complex root system which firms up soil and retains water. They also provide an environment for other needed plants, such as lupines, which fix nitrogen into the soil and they serve as a nutrient and protein-rich feed for cattle.

Too small to sustain enough agriculture to support the entire collective, which consists of some 200 families, the farmers plan to use this plot for multiple ends. They plan to use part of it to experiment with cultivating different grasses, seeing which ones will grow best and can be used to more effectively reforest other mountainsides. Roughly 10 head of cattle will be allowed to graze an enclosed section of the site, whose milk, and meat when needed, will be used by the members of the collective. They may also explore the cultivation of other vegetables. The trees, as stated, will provide firewood to the community.

The Need for More Small Projects

Projects like that at San Mateo reduce demand on the Rimac's waters, provide small communities with greater autonomous water security and reduce the risk of yet more devastating landslides. The Callahuanca hydroelectric plant, a short drive downriver from San Mateo, demonstrates the effects of one such landslide. During the Coastal el Niño, the denuded mountainsides above the plant gave way under heavy rains, washing out houses and rendering the plant inoperable for over a month.  Liz, a resident of neighbouring Puranhuasy , who declined to give her last name, claimed to have never seen mudslides like that in her 36 years of living there. "Power was gone for a week," she said, "and we suffered a plague of insects at night [from the leftover standing water]."

Not far from San Mateo, TNC is also helping the town of San Pedro de Castas to restore and expand a canal system first built by the Inca that will provide more people in that sparsely populated region with clean water. Alejandro Cordova, of the San Mateo farmers collective, plans to use the results of the grass planting experiments to seed more hillsides with grass to stem or even reverse the effects of erosion. With enough projects like this in place, one can imagine a sustainable and secure future for water use in this region.

Challenges to Come

But that future faces challenges. One of the largest and longest running disputes involving the Rimac's water is how to curtail and clean mining-related pollution. A recent study found high doses of sulfides and metals such as arsenic, cadmium, copper, zinc and manganese contaminating the Rimac and Aruri rivers. Although this poses a clear health threat to those using the waters of these rivers, little is being done to remedy it, due to ongoing litigation. While Lima and some towns along the river have treatment plants that can cope with at least some of the mines' pollution, water used for agriculture is rarely treated before use, leading to downstream contamination of produce, livestock and ultimately, people.

Significant changes will have to be made if the water needs of the population dependent upon the Rimac watershed are to be met. Water for everything from agriculture to individual households will need to be used more efficiently. For Lima, this may mean learning to use less water throughout the day. Mining-related pollution must be reined in. Investment in other cities that could stem the flow of migration into Lima would reduce the Rimac's single biggest draw. But these are ambitious proposals that require massive buy-in from citizens, corporations and politicians.

On a smaller but more achievable scale, reforestation and water storage projects like that at San Mateo stand to reduce the demand on the Rimac while empowering local communities and diminishing the chances of future devastating landslides. San Mateo's success is showing a viable way forward that can be copied throughout many other communities along the Rimac River.

Alejandro's dream of saving humanity with his grasses is a pretty big one, but it sounds less naïve looking across the valley that separates San Mateo's water fund from the Coricancha mine. San Mateo's side of the valley is lush and green from the valley floor to its peaks. Trees and bushes stand tall, having benefitted from several years of uninterrupted growth. Across the valley, wide brown landslides scar a mountainside devoid of trees and all but a few hardy quishuar bushes. The view itself is a proof-of-principle for how fitting it is to respond to natural disasters like the Coastal el Niño with natural solutions like San Mateo's promising and easily replicable reforestation project.

This Author

Forest Ray explores social security issues throughout Latin America through the lenses of tourism and ecological health. He is currently based in Cuzco, Peru








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