Fuxianhu lake is located in Yunnan province, southwest of China. It is a deep freshwater lake with a water surface area of 212 km2 and a catchment area of 651 km2. Within the catchment, there exist stream flow, surface runoff and subsurface runoff, which are major sources of incoming water of the lake. These water flows also bring catchment-generated pollutants to the lake. Hydrological processes are complicated in terms of the flow pattern and water exchange between runoffs. In order to accommodate these characteristics and complexities, a hydrological model is proposed based on the concept of "integrated hydrological process". The model takes into account the dynamic water exchange between runoffs and is expected to quantitatively distinguish different types of runoff, and associated pollutants transport. Accordingly, a field observation scheme for rainfall, stream flow and subsurface flow is implemented. Observation data show that rainfall intensity varies significantly across the catchment. Stream flow rate responds rapidly to rainfall showing a typical hydraulic pattern of mountainous streams. Groundwater level is as shallow as less than 2 m deep in some areas. Groundwater level fluctuates in response to rainfall demonstrating a vertical rainfall recharge through the superficial soil. Outcomes from the field data give valuable guidance to further refine the observation scheme, and in long term, will provide hydrological support for model construction and validation.