九州大学学術情報リポジトリ
Kyushu University Institutional Repository
Impact assessment of climate change on habitat suitability, Kikuchi river
レイハネ, モリド
https://doi.org/10.15017/4060149
出版情報：九州大学, 2019, 博士（工学）, 課程博士 バージョン：
権利関係：
（様式２）
氏 名 ：レイハネ モリド
論 文 名 ：Impact assessment of climate change on habitat suitability, Kikuchi
river （菊池川における気候変動によるハビタット適性の評価）
区 分 ：甲
論 文 内 容 の 要 旨
The main purpose of this study is to predict changes in the hydraulic environment due to climate change in the Kikuchi River up to 2080, and to evaluate how fish habitats change. First, I predicted future temperatures and precipitation that would be affected by climate change.
Using two different GCMs, including HadGEM2-ES and MICRO5, under two RCPs (RCP 4.5 and RCP8.5), three 20-year periods (2021-2040, 2041-2060, and 2061- 2080). Next, the effects of climate change on hydrological and environmental parameters were analyzed using the SWAT model and IHA. Furthermore, using the hydraulic calculation model Nays2DH of iRIC(International River Interface Cooperative) software, the influence on hydraulic parameters such as water depth and water velocity was predicted. Finally, the impact of climate change on the habitat of Zacco platypus (Oikawa) and Zacco temminckii (Kawamutsu) was evaluated.
In Chapter 1, I described the background, objectives and procedures of the study.
In Chapter 2, I evaluated how climate change affects meteorological parameters in the Kikuchi River basin. HadGEM2-ES and MICRO5 were used in two different RCPs (RCP4.5 and RCP8.5) to predict changes in rainfall and temperature. The baseline period is 1986-2016 and the forecast periods are 2021-2040, 2041-2060, and 2061-2080. Under HadGEM2-ES, annual rainfall is expected to increase by about 70 mm between 2041-2060 and 50 mm between 2061-2080, and in MICRO5, it will decrease by about 200 mm in 2041-2060 and about 50 mm in 2061-2080 As expected, the increase / decrease was not large, and the result was that there was little change in the annual rainfall. On the other hand, looking at seasonal changes, rainfall in June will increase in the future, and winter rainfall will be almost the same as or less than it is now. The average annual temperature for both models was shown to increase from 15.8 to 18.4 ° C (RCP4.5) and 19.7 ° C (RCP8.5).
In Chapter 3, I used the results of Chapter 2 to estimate the flow rate and evaluate the flow regime. The conversion from rainfall to discharge was performed using a SWAT (Soil and Water Assessment Tool) model as a hydrological model, and the discharge regime was evaluated using IHA (Indicators of Hydrologic Alteration) software. As a result of the future forecast, the average annual flow rate does not change much compared to the present, though there are some differences between HadGEM2-ES and MICRO5. On the other hand, the frequency of extreme low flows and the frequency of high flow pulses were predicted to increase by 60% by 2100.
In Chapter 4, I analyzed how climate change would affect the hydraulic parameters of the Kikuchi River by 2060. Using the results of Chapter 3, iRIC software was used to calculate the water depth and flow velocity in the middle part of the Kikuchi River in January, July and August. The results showed that by 2060 both water depth and current velocity decreased in
January and July, but increased in August.
In Chapter 5, I used the iRIC software EvaTrip solver to analyze the impact of climate change on habitat suitability. Using the results of the previous chapter, the habitat of Kawamutu and Oikawa was evaluated using HIS (Habitat suitability index). Both the juvenile and adult fish have shallower water depths and prefer slow-flowing areas, so the August flow is expected to increase in the future, and the August WUA (Weighted Usable Area) is expected to decrease. On the other hand, the suitability of Kawamutu habitat is not the same between the adult and juvenile stages. Kawamutu does not like low water depth and low flow velocity in the adult stage, but is suitable for the juvenile stage. The river flow in January, which is the adult season, is expected to decrease, and the flow during the juvenile period is expected to increase. In other words, it is expected that it will be difficult to live. On the other hand, water temperatures are predicted to rise up to 5 ° C, which can be considered a threat to both fish species.
In chapter 6, I summarizes the results from Chapter 2 to Chapter 5.
