Clarifying the Lake Water Cycle
Lakes fulfill many vital roles, as water resources, tourism resources, components of ecosystems, etc. However, because various factors are involved, there are also a variety of issues that are likely to have a negative impact that is difficult to rectify, such as deterioration of water quality. When focusing on water, and lakes in particular, it is extremely important to secure both quantity and quality of water for sustainable regional development as they are vital for a region’s daily life, agriculture and industry as well as for outflow of household drainage.
The quantity and quality of lake water are determined by various intake and drainage, inflow of river water and groundwater, runoff of rivers and groundwater, evaporation, etc. Therefore, we must ascertain the temporal and spatial changes in these water cycle processes in order to analyze, understand and predict the quantity and quality of lake water. In this project, we will clarify the water cycle and the resulting lake-water balance of Lake Kasumigaura, a typical example of a lake where eutrophication continues to pollute the water, and Lake Yamanaka, which exists in a volcanic region. To do this, we will observe various water, such as river water, groundwater and evaporation, and collect government data such as rainfall and river flow volume, then analyze and model this information. We also aim to pattern and extrapolate generalities by comparing our results with lake research worldwide.
By combining 10 years of observation at the center of the lake with satellite data, we have clarified the evaporation volume distributed in Lake Kasumigaura, which had not been well-understood. We also conducted interviews and field surveys to clarify the actual conditions of agricultural water intake and drainage. Moving forward, we will clarify changes of Lake Kasumigaura by finding the 10-year averages and comparing them to the results of research conducted in the 1970s.
At Lake Yamanaka, located in a volcanic region, water flows only when it rains in the incoming rivers. This makes inflow and outflow of groundwater especially important. Therefore, we will clarify groundwater flow and the amount of river flow from the river to the lake during rain through both observation and modeling. Additionally, by combining data on water level and river outflow at Lake Yamanaka, we can clarify water cycle change over a period as short as about one month to as long as ten years or more.
Professor, Faculty of Life and Environmental Sciences