Introduction {#Sec1} ============ In 2011, the European Commission published a report on the sustainability of European Union farming systems (European Commission [@CR12]), which emphasised the need to achieve sustainable and multifunctional landscapes. In order to attain sustainability, not only are natural ecosystems and land use management practices preserved but also a diverse range of services provided by both terrestrial and aquatic ecosystems are sustained (European Commission [@CR12]). The ecological status of Europe's waters, characterised by a deterioration of the ecological quality of freshwater, has deteriorated (Sánchez-Somolinos et al. [@CR34]), especially in river basins with significant agricultural areas, and the current situation in agricultural river basins will have implications on freshwater ecosystems for decades to come. Soil erosion is one of the main causes of environmental degradation (Vera [@CR45]). Its direct consequences include a loss of valuable plant and animal species, as well as water bodies, and indirect effects are caused by the loss of soil organic matter and nutrients (Benton et al. [@CR5]). In Europe, 20% of arable land suffers from a soil erosion of more than 30 t ha^−1^ a^−1^ (Kummu et al. [@CR21]) and soil erosion of 60 t ha^−1^ a^−1^ is not an uncommon occurrence in the Netherlands and in central and eastern Europe (van Straaten et al. [@CR47]). As such, soil erosion is a widespread phenomenon in the agricultural production system, regardless of the scale, and it threatens the ecological integrity of water ecosystems (van Straaten et al. [@CR47]). Water pollution and eutrophication are linked to agricultural soil erosion, which reduces the water quality of rivers, as nutrients such as nitrogen and phosphorus, are washed into rivers by overland transport (Benton et al. [@CR5]; Vera [@CR45]). Consequently, river ecosystems degrade and their capacity for self-regeneration is diminished. Nutrient concentrations in rivers, e.g. in Switzerland, are on average four times higher than recommended levels (Schaefer et al. [@CR35]). Soil erosion is one of the main causes of eutrophication (Benton et al. [@CR5]), and as such it has been the subject of numerous studies (de Jonge et al. [@CR10]; Vera [@CR45]; van Straaten et al. [@CR47]). Eutrophication is the most common cause of degraded aquatic ecosystems (Raven et al. [@CR32]) and is associated with harmful algal blooms (HAZs), such as *Microcystis aeruginosa*, *Anabaena flos*-*aquae* and *Aphanizomenon flos*-*aquae*, and an increase in the load of pollutants in water bodies, such as organic carbon, organic nitrogen, phosphorus, heavy metals and nutrients (Conley and Calow [@CR9]; van Straaten et al. [@CR47]). It is estimated that over 75% of freshwaters in Europe are polluted with at least one pollutant or eutrophication indicator (European Environment Agency [@CR11]), and over the last 50 years, the river basin regions in Central Europe have experienced an intensification of agricultural practices with a concurrent decline in river habitats (van Straaten et al. [@CR47]). These phenomena have led to the development of a "eutrophication transition state" in most of Central Europe, and eutrophication is considered a major threat to freshwater ecosystems. On the other hand, in northern European countries eutrophication is not very pronounced, which can be attributed to the high share of agricultural land. In contrast, soil erosion and nutrient runoff in southern Europe lead to a eutrophication state caused by eutrophication and agricultural soil erosion (Benson and Güneri [@CR6]). Despite the increasing emphasis on land management practices in agriculture, the current European legislation offers limited tools for regulating the agricultural production systems to prevent the development of eutrophication problems. The European Water Framework Directive (EC [@CR8]) and the Water Framework Directive (EC [@CR7]) provide a framework for achieving and maintaining a good ecological status of water bodies; nevertheless, the Water Framework Directive is currently being amended in order to better accommodate water quality aspects. As such, water quality legislation is often insufficient to avoid eutrophication. Furthermore, in order to reduce the risk of eutrophication, more effort is needed to reduce nutrient flows from the land to water and to minimise the emission of nutrients and pollutants from agro-industrial processes and wastewater treatment. Economic growth is accompanied by greater pressure on land and resources, which leads to an intensification of agricultural practices and a deterioration of water quality. For example, in the Netherlands, the share of agricultural land was 28% in 1961 and it is expected to decrease to 15% by 2020 (OECD [@CR30]). Agricultural intensification (increase in livestock density, intensification of land use and decrease in the availability of grassland areas) is also associated with a decrease in water quality, mainly by increasing the risk of soil erosion. A decrease in the area of grassland in the Netherlands in recent years led to an increase in soil erosion and the load of nitrogen, phosphorus and pesticides in watercourses, accompanied by a decrease in aquatic biodiversity (de Jonge et al. [@CR10]). In Europe, the impact of intensification and increasing demands for agricultural resources on water quality is still poorly understood. The main problems are (1) increased demand for agricultural resources and the need to preserve limited land resources for nature conservation and water protection, (2) the risk of soil erosion associated with erosion-prone agricultural areas and (3) the increasing pressure on water resources due to the intensification of agricultural practices, which also leads to increased nutrient losses into water courses. The aim of this study was to analyse the relationship between the development of land use in the Netherlands and the quality of water bodies in Europe, as the Netherlands has been recognised as a model country for the development of land use policies (European Commission [@CR13]). Methods {#Sec2} ======= We studied three European river basins, the Rhine, the Maas and the Rijn, located in the North-Western part of the Netherlands (Fig. [1](#Fig1){ref-type="fig"}). These river basins were chosen since their hydrological, morphological, climatic, socioeconomic and cultural settings were similar. Each river basin has a natural inflow and outflow, as the rivers are characterised by the natural flow of rainwater, which reaches the sea with the first rain. This natural inflow and outflow is called groundwater. These watersheds are characterized by a significant human pressure and intensification of agricultural practices, as shown by a comparison with the Netherlands data of 1990 (Statistics Netherlands [@CR41]). In the Netherlands, agricultural land in 1990 was 7.2% of the total area, which is considerably lower than the European average of 16.3%.Fig. 1Location of the three European river basins: Maas, Rijn and Rhine We have selected the period 1971--2012, when there is reliable data on the development of land use in the Netherlands and data on water quality in the selected river basins. For the analysis of the spatial relationship between the land use and the development of water quality, we used GIS software. Characterisation of the surface of land use was carried out by using raster land use data for the whole of the Netherlands (European Land Cover Monitoring Network---Estat-Land [@CR14]), with a horizontal resolution of 1 × 1 km. Land use was characterised as follows: arable land (arable land and pasture, arable land and agriculture not otherwise specified, bare land, barren land, horticulture, permanent crops, and other agriculture); grassland; forest; urban; industrial areas (industrial buildings, quarries and mines; land principally occupied by agriculture) and water (rivers, lakes, reservoirs, reservoirs and ponds, and other bodies of water). Land use is a complex process that depends on land management practices and human activities. In the case of arable land, there are two main processes, which affect the development of soil erosion: (1) soil loss and (2) soil conservation measures. Arable land in the Netherlands is divided into two classes according to the degree of protection from soil loss. Firstly, arable land is a low-risk category, with low intensity of management and limited use of agricultural resources, and secondly, arable land is classified as a high-risk category, characterised by intensive soil management and high intensity of agricultural practices. The area of arable land that was in the high-risk class in 1990 increased by 6.7% over the subsequent 25 years. The increase in arable land area led to the intensification of land use; in other words, a higher rate of the intensification of land use is characteristic of the period from 1990 to 2012. However, during this period, the areas of grassland and forest have decreased, while those of arable land and industrial land increased. Data on water quality was collected by the European Environment Agency. Water quality was measured by the EQR index, which classifies water bodies as to their ability to support human activities (European Environment Agency [@CR11]). The EQR Index is based on seven criteria that evaluate the ecological integrity of river basins: water quantity, water quality, chemical status, habitat quality, biological quality, physical status and human pressures