The Water Quality and Its Criteria for Upland Irrigation System

富营养化湖泊或河流中的蓝藻污染旱地灌溉系统，造成水质恶化，给正常运行带来各种干扰。为了制定相应的设计标准来应对这一困难，我们开展了以下工作：(1)为了分析灌溉系统水质退化的现状，以葛洲里灌溉工程为例，对主要水质指标和流量进行了系统的测量。通过对各项目间关系的统计分析，揭示了水质在系统输送过程中的动态变化过程。在此基础上，估算了作为蓝藻最重要指标的Chl-a的允许浓度。(2)在温室盆栽条件下，研究了灌溉水质对普通荞麦生长和产量的影响。通过一系列试验，确定了蓝藻菌落的水力特性，即藻细胞密度和氧耗量。得到的值将为估算水质负荷和蓝藻的去除效率提供有用的信息。(4)考察了臭氧、紫外线辐射和添加单宁酸等水处理方法对防止或减少蓝藻水华发生的适用性。治疗后的生物活性表示为辐射强度和时间的函数。研究发现，絮体的形成对蓝藻的存活有显著影响。

The contamination of blue-green algae from euntrophic lake or river into upland irrigation system has caused degradation of water quality which will bring about various disturbances for proper operation. In order to establish the design criteria to cope with this difficulty, we carried out the following collaboration.(1) In order to analyze the present situation of water quality degradation in the irrigation system, major items of water quality and flow rate were measured systematically for the case of Kasumigaura Irrigation Project. Statistical analysis on the relation between each items clarified the dynamic process of change of water quality during its transportation through the system. On the basis of this result, allowable concentratioon of Chl-a which can be regarded as the most important index of blue-green algae was estimated.(2) Effects of the quality of irrigation water on the grows and yield of common buckwheat were examined under pot culture in the green house. The result showed no significant change.(3) Hydraulic properties of blue-green algae colony, i.e., the density of algae cell and basic consumption of oxigen were determined by a series of experiments. The obtained value will provide useful information s for the estimation of water quality load and removal efficiency of blue-green algae.(4) The applicability of water treatments by means of an ozonation, an UV radiation and an addition of tannicacid to prevent or to reduce the blooming of algae were examined. Biological activity after treatment were expressed as a function of radiation intensity and elapsed time. It was found that the formation of a floc has remarkable influence on the survival of blue-green algae.