The Science of the Total Environment 292 (2002) 167–176
0048-9697/02/$ - see front matter ᮊ 2002 Elsevier Science B.V. All rights reserved.
Modeling for point–non-point source effluent trading: perspective
of non-point sources regulation in China
W. Zhang*, X.J. Wang
MOE Laboratory for Earth Surface Processes and Department of Urban and Environmental Science, Peking University, 100871,
Beijing, PR China
Received 3 July 2001; accepted 9 November 2001
In the past decades, little abatement efforts have been implemented on China’s non-point source water pollution,
and studies aiming at non-point sources regulation were also rare. Watershed abatement trading between point and
non-point sources may serve as a cost-effective way to deal with the problem. The inherent uncertainty of non-point
emissions, however, could affect the feasibility and outcome of point–non-point effluent trading. The purpose of this
paper is to model the watershed point–non-point abatement trading incorporating the uncertainty of non-point source
emissions, and to examine its impacts on trading equilibrium and trading ratio. The uncertainties of non-point
emissions were taken into consideration by setting an acceptable probability by which the watershed emission
constraints were achieved. Using the watershed optimization model, the optimal abatement allocation and trading
ratio were explicitly illustrated. It was found that they were affected significantly by the variances of non-point
emissions, the reliability requirement assigned to the non-point abatement, and the marginal abatement costs of point
and non-point sources. Since the variances of non-point emissions may increase or decrease at the abatement level,
the impacts of these factors were discussed in different circumstances. Based on the illumination of the trading model,
future directions and implications of point–non-point trading in China were discussed. ᮊ 2002 Elsevier Science B.V.
All rights reserved.
Keywords: Non-point source pollution; Point–non-point effluent trading; Watershed; Uncertainty
The past decades have witnessed some efforts
in point source water pollution controls in China.
Through formulating and carrying out strict regu-
lations and central treatment of urban and indus-
*Corresponding author. Tel.: q86-10-62759190; fax: q86-
E-mail address: email@example.com (W. Zhang).
trial wastewater, problems with conventional
pollutants such as chemical oxygen-demanding
waste and bacteria have lessened. Unfortunately,
the aquatic environmental condition has not
improved commensurately with these point source
controls. Non-point source contributions remain
and have increased as a share of the problem
(SEPA, 1999). China is one of the largest produc-
ers and consumers of chemical fertilizers in the