Outline

  • Abstract
  • Graphical Abstract
  • Keywords
  • 1. Introduction
  • 2. Methods
  • 2.1. Overview of Study Approach
  • 2.2. Study Site
  • 2.3. Land-Use Change Model
  • 2.4. Climate Change Scenarios
  • 2.5. Hydrology and Water Quality Model
  • 3. Results
  • 3.1. Land-Use Change Model Predictions
  • 3.2. Seasonal Change of Water Balance Components Under Baseline Climate Conditions with 2006 Land Use
  • 3.3. Seasonal Change in Water Balance Components Under Multiple Climate Change Scenarios and 2006 Land Use
  • 3.4. Water Quantity and Quality Under Multiple Changes of Land-Use and Climate
  • 4. Discussion
  • 4.1. Impact of Land-Use on Water Quality
  • 4.2. Impact of Climate Changes on Water Quality
  • 4.3. Watershed-Based Mitigation Options
  • 5. Conclusion
  • Acknowledgments
  • Appendix A. Supplementary Data
  • References

رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • 1. مقدمه
  • 2. روش ها
  • 2.1 بازنگری رویکرد مطالعه
  • 2.2 مکان تست
  • 2.3 مدل تغییر کاربری زمین
  • 2.4 سناریو های تغییر جوی
  • 2.5 آب شناسی و مدل کیفیت آب
  • 3. نتایج
  • 3.1 پیش بینی های مدل تغییر کاربری زمین
  • 3.2 تغییرات فصلی اجزای تعادل آب تحت شرایط جوی خط مبناء با کاربری زمین 206
  • 3.3 تغییر فصلی در اجزای توازن آب تحت سناریو های تغییر جوی چند تایی و کاربری زمین 2006
  • 3.4 کمیت و کیفیت آب تحت تغییرات چندگانه کاربری زمین و شرایط جوی
  • 4. بحث و تبادل نظر
  • 4.1 تاثیر کاربری زمین بر کیفیت آب
  • 4.2 تاثیر تغییرات جوی بر کیفیت آب
  • 4.3 گزینه های کاهش مبتنی برآبخیز
  • 5. نتیجه گیری

Abstract

Quantitative prediction of environmental impacts of land-use and climate change scenarios in a watershed can serve as a basis for developing sound watershed management schemes. Water quantity and quality are key environmental indicators which are sensitive to various external perturbations. The aim of this study is to evaluate the impacts of land-use and climate changes on water quantity and quality at watershed scale and to understand relationships between hydrologic components and water quality at that scale under different climate and land-use scenarios. We developed an approach for modeling and examining impacts of land-use and climate change scenarios on the water and nutrient cycles. We used an empirical land-use change model (Conversion of Land Use and its Effects, CLUE) and a watershed hydrology and nutrient model (Soil and Water Assessment Tool, SWAT) for the Teshio River watershed in northern Hokkaido, Japan. Predicted future land-use change (from paddy field to farmland) under baseline climate conditions reduced loads of sediment, total nitrogen (N) and total phosphorous (P) from the watershed to the river. This was attributable to higher nutrient uptake by crops and less nutrient mineralization by microbes, reduced nutrient leaching from soil, and lower water yields on farmland. The climate changes (precipitation and temperature) were projected to have greater impact in increasing surface runoff, lateral flow, groundwater discharge and water yield than would land-use change. Surface runoff especially decreased in April and May and increased in March and September with rising temperature. Under the climate change scenarios, the sediment and nutrient loads increased during the snowmelt and rainy seasons, while N and P uptake by crops increased during the period when fertilizer is normally applied (May through August). The sediment and nutrient loads also increased with increasing winter rainfall because of warming in that season. Organic nutrient mineralization and nutrient leaching increased as well under climate change scenarios. Therefore, we predicted annual water yield, sediment and nutrient loads to increase under climate change scenarios. The sediment and nutrient loads were mainly supplied from agricultural land under land use in each climate change scenario, suggesting that riparian zones and adequate fertilizer management would be a potential mitigation strategy for reducing these negative impacts of land-use and climate changes on water quality. The proposed approach provides a useful source of information for assessing the consequences of hydrology processes and water quality in future land-use and climate change scenarios.

Keywords: - - - -

Conclusions

This study provided a framework that integrated future landuse and climate change scenarios to catchment-scale hydrology models to simulate and assess water quantity and quality. We analyzed the impact of land-use and climate changes on hydrology and water quality in the Teshio River watershed of northern Japan. Our major findings are: (i) the climate changes increased surface runoff, lateral flow and groundwater due to increase in precipitation. The climate changes also increased total N and P yields due to altered hydrological process, fertilizer application and nutrient cycle. Those changes are more strongly than land use changes. (ii) There were strong relationships between hydrologic processes, and fertilizer application and water quality under multiple climate change scenarios, especially via shifting peaks of water, sediment and nutrient yields during the snowmelt and rainy periods. (iii) Loads of N, P and sediment were mainly derived from agricultural land under all land-use and climate change scenarios. The establishment of riparian zones and increase of nutrient efficiency by improved fertilizer application were suggested as possible mitigation options to reduce the nutrient loss from agricultural land under the impacts of land-use and climate changes.

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