Quantitative and Qualitative Pressures on Water Resources

The fact sheet 'Quantitative and Qualitative Pressures on Water Resources' analyses the pressures placed on water resources in terms of water abstraction and pollution in bodies of water.

The knowledge of the rejected and the abstracted volumes on water resources allows us to understand the cause-effect relationship between the state of the water bodies and to assess the best measures directed at these pressures in order to achieve the established environmental objectives.

In order to systematise existing pressures, the following groups are considered:

  • Quantitative pressures: pressures resulting from water abstraction activities for different purposes, namely for the production of water for human consumption, irrigation or industrial activity;
  • Qualitative pressures:
    • Specific: wastewater rejection from urban, domestic and industrial origin or from intensive livestock farms;
    • Diffuse: Rejection of wastewater into the soil, from individual and/or collective septic tanks, intensive livestock farms with agricultural recovery of livestock effluents, extensive livestock farms, agricultural areas, golf courses and mining industries, including abandoned mine sites.
  • Hydromorphological pressures: pressures associated with physical changes to drainage areas, to the beds and margins of watercourses and estuaries with an impact on the morphological conditions and hydrological regimes of water bodies in these categories;
  • Biological pressures: related to pressures of a biological nature, which may have a direct or indirect impact on aquatic ecosystems, such as the introduction of exotic species.

Sustainable water use, particularly in what regards the quantitative aspects, is a real challenge for water resource management, taking into account the current and future uses and their combination with climate change scenarios. In order to respond to this situation, in addition to improving water storage and distribution, measures must be taken in the field of water use efficiency, to promote the reduction of global consumption in areas under greater water stress and to encourage the use of the resulting surplus for other economic activities.

The National Plan for Efficient Water Use (PNUEA) is an instrument that integrates various policies, given the interconnections between power, water, industry and agriculture. Its goal is to reduce water losses and optimise water use as part of measures to protect Water Resources, which is essential in a country where climate variability generates situations characterized by conflicting uses. The PNUEA establishes the targets to be met in terms of water losses per sector by 2020: 20% for the urban sector; 35% for the agricultural sector and 15% for the industrial sector.

The urban sector has made significant investments with the aim of reducing losses from abstraction to distribution, by promoting the use of more efficient technology.

Investments in irrigation infrastructure have contributed to improving water storage and distribution capacity, as well as to promoting the use of more efficient irrigation technologies, thus playing an essential role in reducing the pressure placed upon the environment and in adapting to climate change, which contributes to increasing the competitiveness of agricultural and agri-food companies.

The creation and rehabilitation of collective irrigation infrastructures have played an important role in promoting the efficient use of water, in the creation of renewable energy sources, the preservation of groundwater resources, the maintenance of riparian ecosystems and their environmental functions, soil conservation and increased resilience to forest fires.

On the other hand, qualitative pressures resulting from specific pollution sources on bodies of water are generally related to wastewater rejection from various activities, namely urban, industrial and livestock.

Qualitative pressures associated with diffuse pollution result from the entrainment of natural and anthropogenic pollutants by surface runoff to surface water bodies or by leaching to groundwater bodies. In this context, diffuse pollution can arise from various sources, namely:

•  Excess fertiliser application onto agricultural land;

•  Plant protection products used in agricultural crops;

•  Oils, fats and toxic substances carried by surface runoff from urban areas;

•  Sediment from construction sites;

•  Salts resulting from irrigation and runoff of acid from abandoned mines;

•  Microorganisms and nutrients resulting from the agricultural recovery of livestock effluents.

The methodology used to estimate the pollutant load from diffuse sources arising from agriculture is based on the attribution, to each land-use class, of a capitation corresponding to the diffuse nitrogen and phosphorus loads that will be transported by surface runoff originating in the area that drains into each body of water or group of bodies of water.

Livestock farming is responsible for the production of livestock effluents which, because they contain nitrogen and phosphorus, can be a significant source of pollution, either specific (if discharged into the soil or surface waters) or diffuse (if livestock effluents are applied to agricultural soils in less appropriate ways).

Pollutant loads associated with intensive livestock farms (where livestock effluents are used for agricultural recovery) and extensive livestock farms are considered sources of diffuse pollution due to the entrainment, by surface runoff or leaching, of nitrogen and phosphorus from livestock effluents.

The assessment of the gross nitrogen (N) and phosphorus (P) loads generated by livestock farming began by obtaining the average amount of nutrients excreted annually per livestock unit (CN) for each animal species. The CN values were established in "Decree-Law no. 214/2008 and the number and species/type of animal in each of the farms was obtained from the data of the 2009 Agricultural Census (RA 2009), provided by Statistics Portugal (INE).

The total load generated by each of the farms was evaluated based on the average amount of total nitrogen and phosphates (P2O5) excreted annually per livestock unit, as defined in Decree No. 259/2012.

In order to estimate the total nitrogen and phosphorus loads flowing into bodies of water after their deposition in the soil, the methodological approach used is similar to that considered for calculating the load generated by agricultural and forest areas, which is based on export taxes.

The measures programme is one of the most important parts of the River Basin Management Plan (PGRH), as it sets out the technically and economically feasible actions that will allow attaining or preserving the 'Good' status of waterbodies.

Its definition must be based on the knowledge of cause and effect relationships, using a combined approach, in order to develop management tools that enable the assessment of the environment’s responses and the changes in the pressures exerted upon it, namely by the various socioeconomic activities. It may also imply changes in licensing requisites, as well as a new communication process with the different sectors involved, for the fulfilment of environmental goals.

It is also important to frame the origin of the different sources of funding to be mobilised for implementing the measures programs, such as the national budget, the water resources protection fund, user-generated funds, EU funds and so on. In this respect, it is considered particularly important to ensure a levelled relative financial effort by each of the sources of funding, of the measures programs in Portugal and in the other Member States, particularly Spain.

The measures programme comprises basic measures, supplementary measures and additional measures, adapted to the characteristics of each river basin district and the impact of human activity on the state of the waterbodies, supported by an economic analysis of water uses and by the cost-effectiveness analysis of those measures.

This fact sheet concerns mainland Portugal and shall be updated every 6 years, following the preparation of the River Basin Management Plans.

Objectives and targets: 
  • To know the specific and diffuse pressures affecting each waterbody;
  • To monitor the implementation degree of measures for those pressures;
  • To reduce the impact of these pressures on the state of each waterbody, through the implementation of the measures.
Progress analysis:

With regard to quantitative pressures, the volumes of water abstracted for the various activity sectors (urban, industry, agriculture, livestock, tourism - golf) are presented below.

Last update: 
Tuesday, 27 December, 2016