The Toushe Basin in Yuchi Township, Nantou County, is surrounded by mountains and has a catchment area of approximately 500 hectares. The basin's center is gently sloping, and during rainfall, runoff from all sides converges rapidly into the basin. Surface runoff is primarily drained through the Shuiwei River, with the only outlet at Toushe Bridge. The flat areas in the center of the basin are primarily agricultural or abandoned land, with settlements built around the intersection of the slopes and the basin.
In the past, rice was mostly grown in the Toushe Basin. The "Toushe Rice" at that time was both high-quality and well-known. However, after about 1996, the price of rice was lower than that of other emerging crops, causing farmers to change their target crops. Recently, loofah, which is said to be able to be made into "loofah sago", has become the main crop.
The loofah planting season runs from March to October. Due to the crop's need for irrigation and relatively abundant summer rainfall, the basin's peat soil naturally retains moisture. However, loofahs are not tolerant of waterlogging, so rapid drainage is also a key consideration. As winter approaches, dry farming, short-term crops, or fallow land are common, causing the peat soil to lose moisture for several months. This not only accelerates peat oxidation but also potentially becomes a "carbon source" that escapes into the atmosphere.
From this we can see that although changes in the way humans use basins can increase agricultural returns, they not only change the landscape but may also transform peat soil from a "carbon sink" to a "carbon source."
The coexistence of peat and loofah: both water conservation and flood drainage
The primary solution to the problem of waterlogging in basins is to retain water in peat soils, preventing them from shrinking and causing the ground level to decrease, which would increase the potential for waterlogging. Adjusting agricultural utilization in the basins would not only mitigate the potential for waterlogging but also create opportunities for the loofah industry, which may be facing difficulties with continuous cropping. Why not do this?
Furthermore, "seeking opportunities for the common good" also aligns with the definition of Nature-Based Solutions (NbS). The IUCN (2016) defines NbS as "actions that protect, sustainably manage, and restore natural ecosystems, effectively adapt to and address diverse societal challenges, while providing for human well-being and biodiversity."
"Handcrafted ridges" and "water conservation and soil conservation" are one of the designs that implement NbS in the Toushe Basin while minimizing the impact on existing farming. Another part of this design is the "floating farm."
Water Farms: A Secret Way to Preserve Water and Protect the Land
Over the years, the Water Resources Planning Laboratory of the Water Resources Agency, Ministry of Economic Affairs (hereinafter referred to as the Water Resources Planning Laboratory), has long promoted citizen participation in the Toushe Basin. To address the conflicting demands of drainage and water conservation, it has adjusted the water resources infrastructure and set the goal of "constant water conservation and flood drainage during the flood season while taking into account the sustainability of peat soil and industrial development."
After years of communication and integration, the Institute of Water Resources and Planning collaborated with operators in the Toushe Live Basin Leisure Agriculture Area of Sun Moon Lake to integrate several contiguous fallow fields in the center of the basin for water conservation. Without exposing the peat moss, only topsoil was used to form ridges, which served as water storage spaces. This normally retains water, reducing the risk of the peat moss shrinking and oxidizing due to contact with air, thereby "retaining water and conserving the soil." In addition, simple inlet and outlet flow facilities were installed to control the water storage capacity. This ensures that during rainfall, water can remain in the soil for a longer time, increasing soil moisture content and increasing the infiltration and recharge of groundwater, mitigating the risk of peat moss loss and soil fertility.
Floating farms must also generate production. Island islands and floating platforms can be built along the banks surrounding the reservoir and within its interior to serve as a base for growing aquatic or wetland plants. These plants serve different functions, such as the landscape crop daffodil, the medicinally promising round-leaved knotweed, and the sedge. Floating farms also prioritize biodiversity conservation. For example, the Toushe Basin's native species, the bull dung crucian carp and the scalloped mussel, were relocated during the dry season for conservation and then reintroduced to the floating farm.
Source: Environmental Information Center (https://e-info.org.tw/node/233324)
