1 to 1000 Policy: Controlling Phosphorous Pollution from Tea Farms with Bioretention Cells

Chi-Feng Chen,Hsiu-Feng Liu,Chia-Chun Ho

doi:10.3390/app12052661

Abstract

When implementing nonpoint source pollution control plans, the size or number of required controlling facilities is a very practical issue. However, quantifying nonpoint source pollution is difficult because it is generated by variable and random rainfall events. This study develops a two-stage optimization process to demonstrate the determination of the optimal bioretention cell size for tea farm pollution control. The optimization process was based on a verified watershed-scale model and a verified site-scale model. The verified watershed model was used to obtain total phosphorous (TP) reduction loads. Once the goal of watershed management was decided, the reduction loads were then allocated and the unit reduction loads were determined. Using the unit reduction loads, the verified tea farm model was used to assess the optimal bioretention cell size for tea farms. A case study using the Jinggualiao stream in the Feitsui Reservoir watershed, Taipei, Taiwan was presented. The results showed that the unit tea farm TP reduction loads were 270 g/ha-year and 326 g/ha-year to reach two water quality goals, and a total of 350 m2 and 600 m2 of bioretention cells were needed, respectively. A 1 to 1000 ratio of the standard bioretention cell area to the tea farm area is recommended as a general control rule.

Highlights

Water quality protection is always an important issue, and its implementation relies on comprehensive watershed management work
These structural Best Management Practices (BMPs) are successful in removing different pollutants from surface runoff; how these BMPs contribute to the water quality in receiving waterbodies remains to be demonstrated
The results of the developed optimization process applied to the case study are addressed step by step

Summary

Introduction

Water quality protection is always an important issue, and its implementation relies on comprehensive watershed management work. Directly connecting watershed management control measures and their contributions to water quality improvement is a challenge, especially control measures on nonpoint source pollution [1–4]. The control of nonpoint source pollution is usually difficult, and any associated assessment contains high uncertainty [7–9] This will impede the control of nonpoint source pollution and subsequently weaken the implementation of watershed management policy. Many studies have proven that structural Best Management Practices (BMPs), such as constructed wetlands [10–12], bioretention systems [13–15], grass belts and swales [16] are effective. These structural BMPs are successful in removing different pollutants from surface runoff; how these BMPs contribute to the water quality in receiving waterbodies remains to be demonstrated. The core mission of water quality protection should start with the carry capacity of a receiving waterbody as the foundation of watershed management

Methods

Results

Conclusion