Remediation of nitrate contaminated groundwaters by means of agricultural measures - perspectives of success
Abstract:
Still great lack of knowledge exists concerning the remediation of groundwater con-taminated with nitrate using agricultural measures. This applies for example to the assessment of the efficiency of single agricultural measures as well as to the time scale until these measures take effect in groundwater or in well water. Therefore it was the objective of this project to estimate which levels of nitrate concentration can possibly be achieved in seepage water by different agricultural measures and which time scale for remediation has to be considered. This was based on a compilation of the underlying hydrological and hydrogeological fundamentals. Exemplary the “SchALVO“-ordinance for water protection areas was evaluated, which was enacted in the federal state of Baden-Wuerttemberg in 1988 (last amendment: 2001) to remediate nitrate contaminated groundwater by means of agricultural measures.
A remediation of nitrate contaminated groundwater by agricultural measures in prin-ciple is possible under certain circumstances, even when the catchment area is almost exclusively in agricultural use. Decisions must be based on a detailed survey of the site-specific situation. A remediation expertise should assess the conditions for a successful remediation and show the time in which it can be achieved. Even under auspicious hydrogeological conditions it is usually assumed that a successfully remediation requires up to several years.
Based on the remediation expertise including a risk assessment it is possible to estimate of the chances of success. If it has come to the decision that measures of remediation should be carried out, a catchment management plan on the basis of the expertise has to be implemented as soon as possible.
To ensure a durable success, it is urgently necessary to implement effective remediation measures (e.g. agreements on fertilizing, crop rotation, intercrops, undersown crops, tillage dates) on a big part of the catchment area. To ensure the efficiency of these measures should be accompanied by appropriate monitoring and control. In many cases a change of land use at least in parts of the area may be inevitably (e.g. reduction of the areas of arable land or of the portion of specialized crops, creation of new grassland, set-aside of agricultural land ...).
In some areas one may not reach to remediate the groundwater within a time scale that is acceptable for the water supply. Technical measures must be considered if the result of the assessment is that agricultural or further measures do not lead to success within a reasonable time scale. Changes in well management can be a supporting program to measures in agriculture or land use.
References
KIEFER, J., BALL, T. 2005: Sanierung nitratbelasteter Grundwässer durch landwirtschaftliche Maßnahmen. Veröffentlichungen aus dem Technologiezentrum Wasser, 28 (ISSN: 1434-5765) : 93 - 111; Karlsruhe
