Abstract
The Muroo Reservoir has been used as the source of water supply to Nara city and its neighbouring towns of the Yamato plains and the source of irrigation water. Since the River Uda-gawa being main inflow of the reservoir was polluted remarkably, the water of this lake has been eutrophicated.
In this investigation, we applicated DAIpo value develo ped to assess the water quality of rivers by WATANABE and others (1986) based on the species components of epilithic diatom communities as the biological indicator to monitor the water quality of this reservoir.
The following became clear after the investigation.
The speed of self purification is high at the upper basin and low at the lower in the Muroo reservoir.
The River Temma-g awa have a little flux and high polluted water quality, pollutes the water of this, reservoir again by it's inflow at St.3.
So, we can make a synthetic judgement to the change of water qualities through the water system, e. g. inflow, lake and it's outflow, applicating of DAIpo to the lentic environment.
Synthesizing the re sults of this study and those of WATANABEa nd other's study on several reservoirs, it will be able to classify the system into next three types.
1. W ater quality of the reservoir is nearly same to that of inflow. In these reservoirs, water from inflow stagnate for a short period in the reservoir.
2. Water quality of the reservoir is more inferior than that of in f low. In these reservoirs, water quality of inflow is comparatively clear, and stagnate for a long period in the reservoir.
3. Water quality of the reservoir is m ore clear than that of inflow. In these reservoir, water quality of inflow is high polluted and stagnate fo r a long period in the reservoir.
