Managing forests to improve water supplies
A sound recorder installed on a tree for monitoring bird biodiversity using bioacoustics. Author: Nahia Gartzia Bengoetxea. NEIKER
Mape demonstration site, Urdaibai Biosphere Reserve. Author: Luis Tejido. EFE
Sediments and pathogenic microbes must be removed from raw water to make it safe for human consumption, but disinfection with chlorine leads to the formation of by-products which are harmful to health. Dr Nahia Gartzia-Bengoetxea and her colleagues in the LIFE URBASO project are developing a forest-based solution to naturally reduce the need for water to be treated. The water that comes out of our taps has been treated and purified beforehand to ensure it is safe for human consumption. Typically sediments are removed first with flocculants and coagulants and disinfected after with chlorine. However, treating water with chlorine itself leads to the formation of disinfection byproducts which represent a threat to human health. “Chlorine reacts with the natural organic matter in raw water and produces disinfection by-products like trihalomethanes, potentially carcinogenic substances,” explains Dr Nahia GartziaBengoetxea, a researcher at the NEIKERBasque Institute for Agricultural Research and Development. The amount and quality of natural organic matter in raw water varies according to the environment from which it is abstracted, and Dr GartziaBengoetxea says effective management of the surrounding land might improve the quality of water and so reduce the need to purify it. “We know that managing the area around water abstraction points affects the quantity and quality of the raw water in the abstraction point. This could then have some impact on the treatment that we
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have to apply on the water, and ultimately on human health,” she outlines. This is a topic Dr Gartzia-Bengoetxea is exploring in the EU-backed LIFE URBASO project, in which she and her colleagues are investigating the impact of the continuous cover forestry approach on both water quality and quantity in the surrounding area. The project team are working in the vicinity of Urdaibai Biosphere Reserve in the Basque country, a region in northern Spain that is heavily covered by planted forests. “Most of the surface water abstraction points in the Urdaibai reserve are located in planted forest areas mainly pine and eucalyptus plantations,” says Dr GartziaBengoetxea. These planted forests are typically managed using clearcut forestry practices, which Dr Gartzia-Bengoetxea says leads to an increased risk of soil erosion, which in turn has adverse effects on water quality. “Eucalyptus and pine trees are planted at the same time, then they are all cut together and the cycle starts again. So everything is the same age and species, and all the trees are cut at the same point,” she explains. “This means there is high potential for soil erosion.”
Buffer zones As part of her role in the project Dr GartziaBengoetxea is working to improve the quality of surface water at the abstraction points and so increase the amount of drinking water available, reducing pressure on existing resources. The proposal is to essentially establish four buffer zones around the abstraction points, aiming to protect water from pollution and reduce the need for it to be treated. “The first zone is the riparian buffer zone, which extends 25 metres each side of the river. Then, there are three circular buffers, the first of which extends from the abstraction point until around 100 metres away,” says Dr Gartzia-Bengoetxea. These zones will be managed and protected, with the aim of reducing the amount of sediment in water at the abstraction points, and modulating levels of natural organic matter. “In the zone closest to an abstraction point, we plan to establish native riparian forests to control sediment,” outlines Dr Gartzia-Bengoetxea. “In the second and third protection zones, further away from the abstraction points, we will adopt multifunctional forest management, with a focus on close-to-nature forestry. The primary ecosystem service in these areas is
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