Lugu Lake Ecological Impact Assessment Using Habitat model

Mr. Huang Wei

Abstract

Lugu Lake, which belongs to two provinces, Yunnan and Sichuan Province, is the native place of "The Females' Kingdom" composed of the Mosuo people, a branch of the Naxi nationality. The lake is a very clean and green lake, and there are many kinds of fish, carps and other aquatic species live there. However, with the development of tourism industry, there are more pressures on environmental protection. The water in the lake has been polluted by the untreated sewage discharging into the lake directly. The water quality in the lake begins to turn worse, and the concentrations of Total Phosphorus and Total Nutrient even reached Grade III of the Chinese National Standards for an indefinite period in 2004. The native species in Lugu Lake have declined, and three unique species have become endangered. Therefore, how to keep the water quality and predict habitat distribution change in the future is a significant and important research subject.

Delft3D-WAQ and HABITAT models are used in the Lugu Lake project, but only the Habitat model is focused on this report. Delft3D-WAQ model is run by my colleague Ms Li Yujie (WSE-HI.07-13). The Habitat model will be set up after a Dutch case study is reviewed. Cyprinus Carpio and Ottelia Acuminata are considered as two evaluation species in this Habitat model for Lugu Lake, and the relationship between the two species’ habitats and water quality parameters will be discussed. Water quality parameters, such as, water temperature, water depth, Total Phosphorus, Total Nitrogen and Dissolved Oxygen as the decision rules also are taken account into the model. Those water quality parameters are provided by Delft3D-WAQ modeling. Four assumptions are made in the scenarios:

(i) no pollution falls into the whole lake;

(ii) (ii) only Yunnan province received the pollution;

(iii) (iii) only Sichuan province received the pollution;

(iv) (iv) both two provinces received the pollution. These scenarios will be compared between the year 2006 and 2056.

The study results show that the increase in total nutrient concentration due to Ottelia acuminata species’ habitat suitability decreased in 2006 and 2056, but for Cyprinus carpio, the habitat suitability increased in 2006 and decreased in 2056 since the total phosphorus concentration increased for the pollution fall into the two provinces. Also from the result, it can be seen that the summer maximum water temperature (39°C) is the limiting factor for the two evaluation species.

Key Words: Lugu Lake, Habitat model, Habitat Suitability Index, Habitat Evaluation Procedure, Cyprinus Carpio, Ottelia Acuminata, GIS map, Water Quality Modeling