Water Quantity and Quality Issues in Mediterranean Agriculture - Water and Agriculture: Sustainability, Markets and Policies - page 72

4. Nonpoint pollution control instruments in agriculture

Agricultural nonpoint pollution is a complex issue requiring information on pollution
emissions at the source, transport and fate of pollutants, ambient pollution loads and their
damage costs. Moreover, the physical, economic and social dimensions of the problem
are such that they require multi-disciplinary and multi-scale approaches. In the case of
Spain, nonpoint pollution is currently being addressed by both domestic and European
agricultural and environmental policies. The main current policies are the domestic
National Hydrological Plan and National Irrigation Plan, and the European Union's
Common Agricultural Policy, Water Framework Directive and Nitrates Directive. The
consistency of these policies is far from evident and difficult to assess. An example of
their inconsistency is the nonpoint pollution impact of higher water prices advocated by
the Water Directive, which is discussed below.
The results presented here are limited and do not cover the whole range of factors
affecting agricultural nonpoint pollution. The CAP reform of 2003 and further trade
liberalisation by the EU will change land use patterns in irrigated agriculture at the
extensive and intensive margins. Both abandonment and more intensive use of irrigation
are expected, depending basically on the availability of human and capital resources in
agricultural regions. Thus, more intensive irrigated agriculture is likely in Mediterranean
coastal areas of Spain, while inland collective irrigation areas are expected to stagnate.
Another limitation relates to the range of pollution instruments considered. This is the
case of wetland creation or recovery, which is an efficient instrument for large nitrogen
abatement reductions (Ribaudo el al., 2001). Among the different nonpoint pollution
issues, the information presented here tackles the question of the appropriate base
instrument for nitrogen pollution abatement, which requires accurate information on the
underlying biophysical processes. This is a key question for the design of policy
measures, particularly for the design of the Program of Measures of the Water Directive.
The acute scarcity of information regarding the biophysical processes involved in
pollution and the associated damage costs in Mediterranean agriculture mean that
measures cannot be reliably assessed.
Evaluation of the efficiency of alternative nitrogen abatement measures requires
examination of the biophysical aspects of soil nitrogen dynamics, taking into account
crop type and soil class (Martínez and Albiac, 2004 and 2006). The effects of selected
abatement measures are examined using a dynamic model that includes six crops and one
representative soil, in the Flumen-Monegros irrigation district located in the Ebro basin of
Spain (Table 6). A ranking of nitrogen control instruments by their cost efficiency
contributes to the information needed in the policy decision process. The results are
consistent with previous literature, in suggesting a fertiliser standard as the more efficient
second best measure to control nitrogen pollution (Table 7).

Table 6. Values of key variables under the baseline scenario, by crop

Production
(tons/ha )

Water use
(m 3 /ha)

Nitrogen use
(kg/ha)

Nitrogen leaching
(kg/ha)

Quasi-rent
(

Corn 14.1 6,220 325 140 1,180

Barley 6.0 2,200 180 29 375

Wheat 6.6 3,500 140 32 550

Sunflower 2.9 3,100 70 20 470

Alfalfa 17.3 7,800 70 15 740

Rice 5.6 12,000 170 57 797

Source : Martínez and Albiac (2004).