| The main agricultural economic zone in Sichuan is Red beds hilly area, water shortage and contradiction with water demand over supply are existed in that region. Drinking water in rural areas is mainly distributed in shallow wells, problems such as small in quantity, poor in quality and weak in drought resistance ability are found there. EnYang District belongs to North Sichuan hilly area of typical red beds, water shortage is a major obstacle to the development in EnYang. In recent years, drinking problem in some areas was solved and water shortage was relieved temporarily with well digging projects were put into force in En Yang District. Meanwhile, the system researches of groundwater characteristics and water resources are poor. The paper provides a scientific basis for the rational planning of water resources exploitation by researching the groundwater characteristics and the safety of water resources in En Yang District.Firstly, general situations of study region and the characteristics of red beds are introduced in this paper. Then, the hydrogeologic feature in En Yang District is analyzed from the type and distribution law of groundwater, and relationships between the groundwater recharge, run off and discharge. Next, water situation is analyzed from water quality and quantity. In the end, the safety of water resources in En Yang is researched with hierarchy analysis approach. The water quality is evaluated from the safety of groundwater and drinking water, the comprehensive evaluation method is used to evaluate the safety of groundwater. The water quantity is evaluated from natural recharge capacity which is evaluated with rainfall guaranteed rate, storage capacity which is evaluated with utilization-replacement rate and exploitation amount which is evaluated with utilization rate. The main results obtained in this paper are as follows:(1)Determining the type of groundwater is the three major types of pore water, interlayer fissure water and bedrock fissure water by the groundwater research and the analysis of regional hydro geological report in En Yang District. Pore water in loose layers can be subdivided into the Quaternary system pore water, residual pore water and pore water in colluvial slope.(2)By means of EnYang groundwater recharge, runoff and discharge relationship research, there are mainly pond recharge well, colluvial recharge wells and interlayer fissure recharge well three mode, and the type of ponds recharge to wells is distributed most widely. And relationships between the recharge, run off and discharge of this three types is studied.(3)The pumping tests which cover the main hydrogeological unit were carried out in the water-rich and water-poor sections respectively. The following conclusions are obtained through the analysis of the tests data: The permeability coefficient in water-rich section is 0.1~0.2m/d and water-poor section is 0.012~0.082m/d; The influence radius of water-rich section is 30~55m and water-poor section is 0.3~3.8m.(4)According to the control factors such as landform type and stratigraphic lithologic characteristics in the study area, water storage units in this area are divided into four categories: Water storage unit of Tabular hill type, Narrow valley beam type, Steep inclined single side mountain type and Deep gully hill type. The hydrogeological characteristics and water quantity of all kinds of water storage units are studied.(5)A total of 40 water samples were collected in the study area, 28 samples of them are HCO3-Ca type, 7 samples are HCO3-Ca·Mg type, 2 samples are HCO3-Na·Ca type and one of them is HCO3-Na type. Comprehensive evaluation method was used to evaluate water quality results, and 17 water samples to achieve good and above standards, 23 water samples are poor and range of standards. The standard of drinking water is used to evaluate water quality, and the main unqualified factor is that iron, manganese and ammonia nitrogen exceed the standard.(6)The natural recharge capacity of the study area is 5733×104m3 by the method of rainfall infiltration, the storage capacity is 892.8×104m3 by the volume method and exploitation amount is 406.8×104m3 by the uniformly distributed well method. Under the different methods, the guarantee degree of the water resources in the study area is higher, and the exploitation of the groundwater is reasonable in the near future.(7)Hierarchy analysis approach was used to research the safety of water resource in the paper. Firstly, the safety evaluation index system is established, and the judgement matrix is constructed on the basis of the index system. Then, the relative weight of each index layer on the target layer is calculated with MATLAB, directly establish the safety evaluation standard and determine the safety degree of each index. Finally, comprehensive value of water resources safety assessment is calculated through the weight of each index and equal degree of equal division. Comprehensive value of water resources safety evaluation is 61 in EnYang, to a relatively safe degree, proving it is relatively safe and reasonable to utilize water resources in EnYang District. |
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