Impact of agricultural activity on water resources in Navarre

A group of researchers at the Navarre Public University, together with technical experts from the Navarre Provincial Government, are evaluating the impact of agricultural activity on water resources, based on a Net of Experimental Catchment Areas that the Provincial Administration has installed in several areas of Navarre.

To put this project into effect, the Agricultural Non Point Source Pollution method is being used; AGNPS is a technology which has been developed by the Department of Agriculture of the United States, a body with which the researchers at the Navarre Public University have signed a joint working agreement.

Three Experimental Catchment Areas in Navarre

Obtaining sustainable development is the evermore present objective in society. Agricultural activity is part and parcel of this, given that it has a significant impact on the environment, including, obviously, water resources. From the preliminary studies carried out by the Navarre Government Agriculture Department over more than 20 years, it is known that in Navarre there exist problems of water erosion accelerated by human activity. Once this situation was checked and its extent verified, the need to quantify the problem was tackled.

To this end, in 1994, the Navarre Government began to Net of Experimental Agricultural Catchment Areas representative of the most relevant usage and management of water resources in the Provincial Community. Currently this Net consists of three Catchment Areas: Latxaga, La Tejería and Oskotz. The first two are representative of the semiarid cereal crop conditions of the Midlands Zone of Navarre, where there is an attempt to identify problems of shifting earth together with other problems of normal agricultural activity such as contamination by agricultural chemicals. Later on in the study we looked for more humid terrain, where we could investigate the impact of pastoral farming. Moreover, to complete the research, a further type of representative catchment area is studied. For example, a vine-growing area in the south and another under irrigation, which would be representative, respectively, of Midlands Navarre and the Ribera (the Ebro river basin).

Each one of these catchment areas has a complete automatic meteorological station with data registration storage every ten minutes (various totaliser pluviometers) and one or two capacity measurement stations in which, apart from registering capacity data every ten minutes, information on water quality is registered, through taking samples of the water deposits.

The general aim is to collect, store and analyse data of the first estimates of soil loss in crop cultivation areas as well as the impact of agriculture on the quality of runoff. But also we have followed the technique suggested by the Navarre Department of Agriculture involving the need to interpret this data and draw conclusions that enable us to obtain information about the processes and tendencies over larger areas, over longer time periods and about the responses of the systems under different conditions. This is where the researchers from the Navarre Public University came in.

Models of cutting edge technology

Although there are numerous models capable of simulating the hydrological behaviour of water catchment areas – for different ends and these can be useful for understanding the cause-effect relationships amongst these -, the AGNPS model is one of the most complete and powerful tools for the study of hydrological, contaminant and erosive effects derived from agricultural and forestry activity.

The model is a distributive one which operates on an on-going, daily basis and which was developed in order to simulate the long-term transport of sediments and agricultural chemicals in large, unmonitored agricultural basins. The generation and circulation of runoff water and the transport of sediments, nutrients and pesticides are its fundamental components. It is model which enables the definition in a detailed manner of the characteristics of each zone within the catchment area or basin being studied, as it splits this up in more or less homogeneous areas (cells), connected to the drainage network. AGNPS measures and records the amount of runoff water and contaminants provided by each cell to the exutoria of the catchment area, which helps management personnel to identify these problem areas, thus enabling them to concentrate on corrective action more efficaciously.

Finally, we should take into account that, in the United States, the AGNPS model is currently a practical application tool, the results will be transmitted to the relevant bodies with the aim of deciding on possible lines of work regarding the better use and management of terrain, based on the experimental data and the simulations carried out.