This paper uses an economic catchment model to assess changes in land use, enterprise distribution, greenhouse gas emissions and nutrient loading levels from a series of policies that introduce carbon prices or nutrient reduction caps on land-based production in the Hurunui Catchment in Canterbury, New Zealand. At $20/tCO2e, net revenue for the catchment is reduced by 7% from baseline levels while GHGs are reduced by 3%. At $40/ tCO2e, net revenue is reduced by 15% while GHGs are reduced by 21%. Nitrogen and phosphorous loading levels within the catchment were also reduced when landowners face a carbon price, thus providing other benefits to the environment. Additional scenarios in this paper assess the impacts from developing a large-scale irrigation project within the catchment. Results show that while adding irrigation can improve farm output and revenue, it also results in dramatically higher GHG emissions and nutrient loads. Placing a carbon price on land-based activities diminishes some of these pollutants, but not at the same rate as when the policy what enacted on the baseline irrigation levels. Finally, we investigate the impacts of imposing a nutrient loading cap on farm activities instead of a carbon price and find that if landowners had greater access to irrigation but were constrained to hold the nutrient loads at baseline levels, revenue could increase by 6% over the baseline while GHG emissions could be reduced by 5%. Our findings suggest that while there is a potentially a strong trade-off between water quantity and water quality in the Hurunui Catchment, imposing the right policy levers could reduce some of the environmental impacts from an increase in land-use intensity without placing a large economic or regulatory burden on its landowners.

本文使用一个经济流域模型来评估土地利用、企业分布、温室气体排放和养分负荷水平的变化，这些变化来自于在新西兰坎特伯雷的Hurunui流域对陆地生产引入碳价格或养分减少上限的一系列政策。在20美元/千吨二氧化碳当量的情况下，该流域的净收入比基线水平减少了7%，温室气体减少了3%。以每吨二氧化碳40美元的价格计算，净收益减少了15%，而温室气体减少了21%。当土地所有者面临碳价格时，流域内的氮和磷负荷水平也降低了，从而为环境提供了其他好处。本文中的其他场景评估了在流域内发展大规模灌溉项目的影响。结果表明，虽然增加灌溉可以提高农业产量和收入，但也会导致温室气体排放和养分负荷显著增加。对以陆地为基础的活动设定碳价格可以减少其中一些污染物，但其速度与对基线灌溉水平制定政策的速度不同。最后,我们调查的影响实施营养负荷上限农场活动而不是碳价格,发现如果地主大灌溉,但受到限制的营养负荷在基线水平,在基线收入将增长6%,而温室气体排放将减少5%。我们的研究结果表明,虽然有一个潜在的强大的水量与水质之间的权衡Hurunui流域,实施正确的政策杠杆可以减少一些环境影响的土地利用强度的增加而不会将一个大地主经济或监管负担。