GB/T 51040-2023Technical standard for groundwater monitoring (English PDF)

1 General provisions

1.0.1 The standard was drawn up in order to suit the needs of the development of groundwater monitoring, to raise the quality and technical level of the construction and operation of groundwater monitoring works, to meet the needs of groundwater survey and planning, water saving and protection, the control of over-exploitation, pollution prevention and control and supervisory management, and to be technically advanced and economically reasonable.

1.0.2 The standard applies to the design, construction and acceptance of groundwater monitoring works and to the operation and maintenance of monitoring systems.

1.0.3 Besides this standard, groundwater monitoring works shall also comply with the provisions of the relevant national standards in force.

2 Terms

2.0.1 Groundwater monitoring station: the monitoring facilities and equipment set up to obtain monitoring information such as groundwater level, water temperature, volume abstracted, spring discharge and water quality, consisting mainly of monitoring facilities, monitoring instruments and equipment and ancillary facilities.

2.0.2 Groundwater monitoring: the process of monitoring and surveying the regime elements of groundwater, such as water level, water temperature, water quantity and water quality, through groundwater monitoring stations at the prescribed time intervals and to the prescribed accuracy; in this standard it also means information monitoring.

2.0.3 Measuring point: the fixed point set on the head of a groundwater monitoring well or on an ancillary facility for measuring the groundwater level or the depth to water, being the starting point of the measurement of level or depth.

2.0.4 Groundwater level: the elevation of the free water surface of the groundwater in a monitoring well.

2.0.5 Depth to water table: the vertical distance from the free water surface of the groundwater in a monitoring well to the ground at the well head.

2.0.6 Difference of groundwater level between two measurements: the difference between the current monitored value of groundwater level or depth to water and the value monitored on another occasion.

2.0.7 Groundwater regime: the phenomena and processes by which the elements of groundwater, such as water level, water temperature, water quantity and water quality, change with time.

2.0.8 Groundwater data processing: the collective name for the work of sorting, analysing, checking, compiling and publishing or storing original groundwater monitoring data.

2.0.9 Permeability sensitivity test of monitoring well: the hydrogeological test work of injecting water into a monitoring well and observing the recovery of the water level, so as to judge whether the permeability of the well wall has changed markedly.

2.0.10 Hydrogeological conditions: the collective name for the burial, distribution, recharge, runoff and discharge conditions of groundwater, its quantity and quality and the geological conditions under which it is formed.

2.0.11 Hydrogeological unit: a groundwater system with unified boundaries and unified recharge, runoff and discharge conditions.

2.0.12 Type division of groundwater monitoring: the areas divided according to landform, geological background and ecological environment, hydrogeological conditions and the intensity of groundwater development and use, as required by the work of groundwater monitoring.

2.0.13 Phreatic water: groundwater buried above the first stable aquiclude below the ground surface and having a free water surface.

2.0.14 Confined water: groundwater filling the space between an upper and a lower relative aquiclude and subject to hydrostatic pressure.

2.0.15 Renewable groundwater: groundwater having a direct recharge and discharge relation with local atmospheric precipitation or with surface water bodies, including phreatic water and confined water closely connected hydraulically with phreatic water.

2.0.16 Unrenewable groundwater: groundwater that in the natural state has a weak hydraulic connection with other water bodies and cannot be renewed or is hard to renew.

2.0.17 Intensity of groundwater development: the ratio of the actual volume of groundwater abstracted within an area to the exploitable volume, usually expressed as a percentage.

2.0.18 Groundwater over-exploitation area: an area in which, over a given period and within a given region, the actual volume of groundwater abstracted exceeds the exploitable volume, or in which groundwater abstraction causes the groundwater level to fall continuously, or in which ecological and geo-environmental problems arise.

3 Monitoring network planning and layout

3.1.1 Groundwater monitoring type areas may be divided into basic type areas and special type areas, and shall comply with the following. Basic type areas may be graded as follows: first-order basic type areas may be divided, according to the regional landform, into hill areas and plain areas; second-order basic type areas may be divided, according to the secondary landform and the lithology, so that plain areas fall into alluvial-pluvial-lacustrine plain areas, intermontane plain areas, inland basin plain areas, loess plateau areas and desert areas, and hill areas fall into ordinary bedrock hill areas, karst mountain areas and hilly areas; third-order basic type areas may divide the second-order basic type areas further into a number of hydrogeological units according to the hydrogeological conditions. Built-up urban areas, large groundwater source areas, groundwater over-exploitation areas, areas of sea-water and saline-water intrusion, areas of land subsidence and ground fissures, areas of groundwater pollution and pollution risk, ecologically fragile areas, water conservation areas, areas of secondary salinisation, areas of karst collapse and areas of ecological water replenishment, including riverside abstraction areas, shall be divided as special type areas. A basic type area and a special type area, or different special type areas, may contain one another. Where a basic type area and a special type area overlap, the classification shall follow the type area with the highest network density.

3.1.2 Basic groundwater type areas shall be divided into three classes of intensity of development and use, namely weak, medium and strong, according to the intensity of groundwater development.

3.2.1 Groundwater monitoring stations should be divided, according to the purpose and function of the monitoring service, into basic stations, special stations, simultaneous monitoring stations and experimental stations. Basic stations should be divided, according to the element monitored, into water level and water temperature basic stations, abstraction volume or discharge basic stations, and water quality basic stations.

3.2.2 Groundwater monitoring stations should be divided, according to the level of administration, into national, provincial and prefecture or municipal monitoring stations.

3.3.1 The planning of the monitoring network shall comply with the following: it shall be carried out within the planning horizon year according to the demand for groundwater monitoring arising from groundwater survey and planning, water saving and protection, the control of over-exploitation, pollution prevention and control and supervisory management, combined with economic and technical conditions; a unified national groundwater monitoring network shall be set up and local network plans shall be coordinated so that the functions of monitoring networks are not duplicated; monitoring stations shall be laid out in administrative divisions at county level and above, and the density of the network should suit the local management needs; the layout shall take account together of new and rebuilt stations, shallow and deep aquifers, plain and hill areas and basic and special types, and the layout shall be concentrated on special type areas such as groundwater over-exploitation areas.

3.3.2 The planning of the monitoring network shall cover the following main items: collection of the historical monitoring network, of monitoring and evaluation data, of hydrogeological data and of groundwater and other planning results, with site reconnaissance and special investigation to be carried out where such data are not enough for the planning; evaluation of the present state of monitoring and analysis of the demand for monitoring, so as to settle the planning demand; the objectives, basis, extent and horizon year of the monitoring plan; the network density, the position and function of the stations, the type of station and the elements monitored; the information flow, the technical methods of information collection and transmission, the way information is shared and exchanged, the methods of receiving and processing information and the construction of the information service system; typical designs for new and rebuilt stations; analysis of the economic, social and environmental benefits; and the investment estimate.

3.4.1 Monitoring stations shall be laid out throughout the alluvial-pluvial-lacustrine plain areas, the intermontane plain areas and the inland basin plain areas among the basic type areas; in the hill areas among the basic type areas and in the loess plateau areas and desert areas among the plain areas, typical representative areas shall be chosen for the layout of monitoring stations; in special type areas the monitoring stations may be made denser as needed. The monitoring stations laid out in basic type areas and special type areas shall meet the needs of water resources management in each county-level administrative division.

3.4.2 Monitoring stations shall be laid out reasonably: in plan they shall combine points, lines and areas; in the vertical direction the layers shall be clearly separated and monitoring shall be carried out layer by layer; one station should serve several purposes; and existing wells and boreholes that meet the monitoring conditions should be chosen.

3.5.1 The layout of water level basic stations by county-level administrative division shall comply with the following: a county mainly of plain area shall have 5 to 10 water level basic stations, southern regions taking the middle to lower values and northern regions the middle to upper values; a county mainly of hill area shall have 1 to 5 water level basic stations, a county with a smaller population and weaker management needs taking the middle to lower values and a county with a larger population and greater management needs the middle to upper values; where the water level basic stations laid out by county-level administrative division cannot meet the management needs, the layout shall be controlled by the density per hydrogeological unit.

3.5.2 The layout of water level basic stations by hydrogeological unit shall comply with the following: in basic type areas the basic stations shall be laid out mainly along the direction of groundwater flow and secondarily perpendicular to it, while in special type areas the basic stations shall be laid out according to the particular hydrogeological conditions; the layout density of groundwater level basic stations in basic type areas shall comply with Table 3.5.2-1; the layout density of basic stations in special type areas shall comply with Table 3.5.2-2, and in a hydrogeological unit where both shallow and deep over-exploitation areas exist the layout shall be made separately for the shallow and the deep aquifer with the densities of Table 3.5.2-2; where there are several confined aquifer groups, monitoring should be carried out layer by layer, and the station density of each layer group shall be taken according to the basic type area or the special type area; in very large and super-large cities or in management areas with a need for fine groundwater management, the density of basic stations shall be increased above the related network density; in areas with complex hydrogeological conditions the density of basic stations should be increased, and in areas where special type areas overlap the density of basic stations may be increased; where a production well or a village well is used as a water level basic station, a well with no pump inside and with fairly complete well completion records shall be chosen.

Table 3.5.2-1 fixes the layout density of groundwater level basic stations in basic type areas, in stations per 1000 km2. Its rows are the first-order, second-order and third-order basic type area names, from the alluvial-pluvial-lacustrine plain areas down to the loess and bedrock hilly areas, and its columns give the form of layout, which is either a full layout or a layout in chosen typical representative areas, and a density range for each of the three intensities of development, weak, medium and strong. The individual density ranges are not reproduced here, because the table runs across two pages with several merged row groups and the pairing of rows to values could not be verified with certainty on the scan. The note column of the table is legible and states that the intensity of groundwater development is expressed by the abstraction coefficient K with subscript c, the ratio of the volume abstracted to the exploitable volume, and that the intensity may be divided into four classes: weak abstraction area, K with subscript c less than 0.3; medium abstraction area, K with subscript c from 0.3 to 0.7; strong abstraction area, K with subscript c from 0.7 to 1.0; and over-exploitation area, K with subscript c greater than 1.

Table 3.5.2-2 fixes the layout density of groundwater level basic stations in special type areas, in stations per 1000 km2. The rows legible on the pages examined are: built-up urban area, 15 to 50; large groundwater source area, 15 to 35; and groundwater over-exploitation area, split into ordinary over-exploitation area, 15 to 40, and severe over-exploitation area, 30 to 60. The table continues beyond the last page examined.