GB/T 50625-2023Technical standard for water wells (English PDF)

1 General provisions

1.0.1 The standard was drawn up in order to unify the technical requirements for the construction and management of water well works, to secure the quality and safety of water well construction, to raise the level of management, to bring out the full benefit of the works, and to achieve sustainable development and use of groundwater resources together with protection of the groundwater environment.

1.0.2 The standard applies to the planning, design, construction, ancillary equipment, acceptance, rebuilding, repair and abandonment of water wells for agricultural, industrial and domestic water supply.

1.0.3 The planning and design of water wells shall be carried out on the basis of a hydrogeological survey and an evaluation of groundwater resources.

1.0.4 The materials used in a water well shall be free of pollution and non-toxic.

1.0.5 A water well shall be put into use only after it has passed acceptance.

1.0.6 Records shall be kept for a water well project.

1.0.7 A water well that has been abandoned or has finished its service function shall be backfilled or sealed, and the work shall be recorded and filed. A water well that has been sealed shall be given a permanent marker.

1.0.8 Besides this standard, the planning, design, construction, ancillary equipment, acceptance, rebuilding, repair and abandonment of water wells shall also comply with the provisions of the relevant national standards in force.

2 Terms

2.0.1 Water well: a well from which water is lifted by a pump driven by a power machine.

2.0.2 Tube well: a well more than 10 m deep with a well diameter of 50 mm to 1000 mm, made up of the well head, the casing pipe, the screen and the sediment pipe.

2.0.3 Large opening well: a well with a diameter greater than 1 m.

2.0.4 Radial well: a well fitted with transverse radial pipes or holes.

2.0.5 Limited well-screen entrance velocity: the maximum permissible velocity at which groundwater enters the screen.

2.0.6 Limited well-bore seepage velocity: the maximum permissible velocity at which groundwater enters the bore from the aquifer.

2.0.7 Tube well structure: the technical elements forming the columnar section of a tube well, including the depth of the well, the diameter of each well section, the diameter and length of the well pipe, the gravel pack and the sealing positions.

2.0.8 Bore diameter: the diameter of the cross-section of the bore, including the starting diameter and the final diameter.

2.0.9 Well diameter: the diameter of the cross-section of the well.

2.0.10 Well pipe: the collective name for casing pipe, screen pipe and sediment pipe.

2.0.11 Casing pipe: a seamless pipe without holes that supports and seals the well wall.

2.0.12 Sediment pipe: a seamless pipe without holes at the bottom of the well in which sand grains and sediment settle.

2.0.13 Well screen: the device placed in the production section that filters the water, holds back sand and protects the wall.

2.0.14 Screen pipe: the skeleton pipe of the screen, called the water-filtering pipe for short; when used on its own it is also called the screen.

2.0.15 Gravel pack: solid particles of given size, grading and hardness that fill the annular gap between the screen pipe and the bore wall.

2.0.16 Gravel-packed screen: a screen with gravel pack of a given specification filled around the outside of the screen pipe.

2.0.17 Non-gravel-packed screen: a screen with no gravel pack.

2.0.18 Gravel-precoated screen: a screen made by bonding gravel with an adhesive onto a skeleton pipe of steel, plastic or other material.

2.0.19 Prepacked gravel screen: a screen made by filling gravel of a given grain size into the annular gap between an inner and an outer screen pipe.

2.0.20 Wire-wound screen: a screen wound with wire of a given specification and having a given porosity.

2.0.21 Bridge slot screen pipe: a screen pipe made by punching a steel sheet so that the punched parts stand out from the wall as bridge-shaped ridges with two vertical slots on the two sides of the bridge, then rolling the sheet into a tube and welding it.

2.0.22 V wire wrap screen pipe: a screen pipe made from several longitudinal support bars of triangular, trapezoidal or circular section, wound circumferentially with wire of triangular or trapezoidal section and welded at the crossing points of the longitudinal bars and the circumferential wire so as to leave a given void; also called a Johnson pipe.

2.0.23 Aperture ratio of screen pipe: the ratio of the total area of the holes or slots of the screen pipe to the outer surface area of the screen pipe.

2.0.24 Porosity of screen: the collective name for the porosity of the outer inlet face of the screen and its effective porosity.

2.0.25 Flushing medium: the substance used during drilling to carry the cuttings, clean the bottom of the hole, cool and lubricate the drilling tools and protect the bore wall.

2.0.26 Well completion technology: the construction processes carried out after the drilling of a water well is finished, namely well probing, mud replacement, well pipe installation, gravel packing and sealing, together with well flushing, the pumping test and the collection of water samples.

2.0.27 Gravel packing: the process of placing gravel of the specified grade into the annular space between the screen pipe and the bore wall.

2.0.28 Sealing: the process of using impervious material and the related measures outside the well pipe to stop the hydraulic connection between the layer targeted for abstraction or recharge and the other strata.

2.0.29 Well flushing: the process of removing the flushing medium, silt and cuttings from inside and outside the well, opening up the aquifer and raising the permeability around the tube well.

2.0.30 Pumping test: a field hydrogeological test in which water is pumped from the well to determine its yield capacity, to check the quality of the sealing and of the well flushing, to obtain the hydrogeological parameters of the aquifer and to establish the hydrogeological conditions.

2.0.31 Design discharge of water well: the discharge that keeps a water well in normal operation over its service life.

3 Planning for water wells

3.1.1 The planning of water wells shall comply with the relevant plans, such as the integrated water resources plan for the basin and the region and the plan for the development, use and protection of groundwater, and shall suit the needs of near-term and long-term social and economic development and of ecological and environmental protection within the planning area.

3.1.2 An evaluation of groundwater resources shall be carried out before water wells are planned. The evaluation shall comply with the relevant provisions of the industry standard SL/T 238 in force, and the analysis of water demand and of supply against demand shall comply with the relevant provisions of the industry standard SL 429 in force.

3.1.3 A water source area shall be placed in a water-rich zone where quantity and quality are secured and where protection of the groundwater environment is easy to carry out.

3.1.4 Hydrogeological data for groundwater abstraction shall be obtained as laid down in the national standard GB 50027 and the industry standard SL 454 in force; shallow groundwater should be abstracted and the abstraction of deep groundwater shall be controlled.

3.1.5 Abstraction of groundwater in an over-exploited area shall comply with the relevant provisions of the national standard GB/T 34968 in force. In a restricted abstraction area the addition of new wells and the volume of groundwater abstracted shall be controlled; in a prohibited abstraction area no new well may be added.

3.1.6 Groundwater abstraction shall be monitored and managed. Water-saving techniques and equipment shall be used where groundwater is taken.

3.1.7 The quality of irrigation water shall comply with the relevant provisions of the national standard GB 5084 in force; the quality of domestic water shall comply with the relevant provisions of the national standard GB 5749 in force; the quality of industrial water shall comply with the national provisions in force for industrial process water.

3.1.8 The layout of groundwater monitoring stations shall comply with the relevant provisions of the national standards GB 50027 and GB/T 51040 in force.

3.1.9 Protection of groundwater in the planning of water wells shall comply with the following: within the planning area the wells shall be kept away from existing sources of pollution and the water source area shall be sited upstream of the sources of pollution; no facility that pollutes groundwater may be built within the planning area or the water source area; a drinking water source protection zone shall comply with the provisions of the industry standard HJ 338 in force.

3.2.1 The basic data for the planning of water wells shall cover physical geography, social and economic conditions, the ecological environment, engineering geological and hydrogeological conditions, the present state of development and use of groundwater and surface water resources, and the evaluation of groundwater resources.

3.2.2 The basic data for the planning of water wells shall be reliable, reasonable and consistent, and shall be results that have been compiled and reviewed.

3.2.3 The basic data on physical geography shall cover geographical position and landform; soil type, precipitation, evaporation, air temperature, frost-free period and depth of the frozen layer; surface runoff and the record of flood and drought disasters.

3.2.4 The basic data on social and economic conditions shall cover the area, population, income per head and gross national product of the planning area; the structure and layout of industry and agriculture; and the present state of development of energy, transport, urban and rural construction and the environment.

3.2.5 The basic data on the ecological environment shall cover the present state of the ecosystem within the planning area together with ecological protection and ecological problems; the state of the surface vegetation; and the sources, distribution and state of pollution of groundwater and surface water.

3.2.6 The basic data on engineering geological and hydrogeological conditions shall cover the geological structure and the distribution and features of the strata and their lithology; the type of groundwater and the thickness, distribution, burial and abstraction conditions of the aquifers or aquifer groups; the recharge, runoff and discharge conditions of the groundwater; the regime of the groundwater and the hydraulic connection and mutual recharge among the aquifers; and the chemical types, features and pattern of change of the groundwater.

3.2.7 The basic data on the development and use of groundwater and surface water resources shall cover the number and distribution of wells already built, their ancillary equipment, their rate of use and their rate of good condition; the present volume of groundwater abstraction for agriculture, industry and domestic use within the planning area; water quotas, the water use regime, water use techniques and the irrigation water use coefficient; and the number, present state, benefit and use of surface water works and facilities.

3.2.8 The data on the evaluation of groundwater resources shall cover the calculation and evaluation of the recharge, discharge and exploitable volumes of groundwater together with an analysis of their distribution in space and time; the evaluation of groundwater quality; and an analysis of the effect of human activity on groundwater resources.

3.3.1 Water wells shall be placed in areas where groundwater is plentiful, easy to abstract and of good quality in the aquifer. The layout of wells should also take account of the completeness of the administrative divisions and should make use of existing facilities such as roads and the power grid.

3.3.2 The type of water well shall be chosen economically and reasonably according to the hydrogeological conditions of the planning area or the water source area and according to the water demand.

3.3.3 A tube well may be used to abstract groundwater from unconsolidated aquifers and from bedrock aquifers at any depth of burial.

3.3.4 A large opening well should be placed in the following areas: piedmont alluvial fans where groundwater is shallow, recharge sources are plentiful and the aquifer is highly permeable, and flood plains and first terraces where the underflow of the river bed is plentiful; and sections where the weathered fissure layer of the bedrock is fairly thick, surface karst is developed, groundwater is shallow and recharge sources are plentiful.

3.3.5 A radial well should be placed in the following areas: coarse sand, gravel and cobble aquifers where groundwater is shallow and recharge sources exist, and silty, fine and medium sand aquifers developed within 30 m of depth; piedmont alluvial fans, flood plains and first terraces where groundwater is shallow, and riverside sections where the well can extend into the aquifer under a river, lake or other water body to collect infiltrated water; and loess fissure aquifers with developed fissures and a thickness greater than 20 m.

3.3.6 The layout of a well group shall be settled from the thickness and number of aquifers, the direction of groundwater flow, the water-storing structure, the landform and the other engineering geological and hydrogeological conditions of the planning area or the water source area. Square, triangular, circular-arc and linear patterns may be used; a group of radial wells or large opening wells taking water beside a river should be laid out in a single row parallel to the river. A safe distance shall be kept between the well positions and buildings or structures.

3.3.7 Where a group of wells supplies industrial or domestic water, standby wells shall be provided. The number of standby wells should be set at 10 % to 20 % of the design water volume, and there shall be not fewer than one standby tube well.

3.3.8 The well spacing and the number of wells for irrigation shall be settled as follows. The preliminary well spacing may be calculated with the formulas given in the standard, one for a square well pattern and one for an equilateral triangular well pattern, together with a formula for the irrigation area controlled by a single well. In those formulas the symbols are: L with subscript zero, the well spacing in m; F with subscript zero, the irrigation area controlled by a single well in hm2; Q with subscript zero, the design discharge of a single well in m3/h; t with subscript d, the number of hours of operation per day during the irrigation period in h/d, which should not be lower than 16 h/d; T with subscript c, the number of days in each rotational irrigation period in d; the Greek letter eta, the irrigation water use coefficient; eta with subscript one, the water reduction coefficient; and m, the combined average irrigation quota in m3/hm2. The preliminary well spacing shall then be checked by the interference pumping method or by the analogy method, according to the particular conditions of the planning area; after the check, the average water reduction coefficient from interference among the wells should not be greater than 0.20. The number of wells may be calculated either by the method of the irrigation area controlled by a single well or by the exploitable modulus method; in those formulas N is the number of wells, F is the irrigation area of the planning area in hm2, M is the exploitable modulus within one year in m3 per km2 per year, and T with subscript a is the number of irrigation days in one year in d/a. The equations themselves are printed as formulas and are not reproduced here.

3.3.9 The well spacing and the number of wells for a water source area supplying industrial and domestic water should be chosen by the interference pumping method or by the analogy method.

4 Design for water wells

4.1.1 The design of a water well shall collect the relevant data for the area where the well is to be built, and a site reconnaissance shall be carried out.

4.1.2 The design of a water well shall take account of the plan, the intended use, the water supply volume, the water quality requirements, the hydrogeological conditions, the extent of the area where the well is to be built and any special requirements of the user.

4.1.3 When a group of water wells is designed, a long-term observation network shall be laid out at the same time. The layout of the long-term groundwater observation network and the design of the long-term observation holes shall comply with the relevant provisions of the national standards GB 50027 and GB/T 51040 in force.

4.2.1 The design discharge of a single well shall be settled from the hydrogeological conditions, the design well type and the design drawdown of the water level, using either theoretical calculation or the discharge-drawdown curve of a pumping test. The formula for the discharge shall be chosen reasonably according to the hydrogeological conditions, and the formulas of Appendix A of the standard may also be used.

4.2.2 The design discharge of a well group shall be settled from the hydrogeological conditions, the design well type, the design drawdown of the water level, the layout of the wells and the water reduction coefficient of the mutual interference. The water reduction coefficient for the different well spacings shall be settled jointly from single-well pumping tests and interference pumping tests according to the layout of the wells. The total design discharge of a well group shall be smaller than the exploitable volume of groundwater of the planning area.

4.2.3 Where data are insufficient, the design discharge of a water well may be settled from measured data of exploration and production wells or from data on water wells under similar conditions nearby.

4.2.4 The design discharge of a water well shall be smaller than the yield capacity of the well, and the yield capacity of the well is limited by the permissible entrance velocity of the screen and by the permissible seepage velocity at the bore wall. The design discharge shall be checked against the permissible inflow of the screen and the permissible inflow at the bore wall. For the first check the standard gives one general formula together with a formula for the effective inflow area of a tube well, one for a large opening well and one for a radial well. The symbols of those formulas are: Q, the design discharge of a single well in m3/s; Q with subscript g, the permissible inflow of the screen in m3/s; P, the effective porosity of the inlet face of the screen in %, which for a tube well should be taken as 50 % of the porosity of the screen face, for a large opening well as 80 % to 100 % of the porosity of the filtering structure, and for a radial well as 80 % to 100 % of the porosity of the face of the radial pipe; v with subscript g, the permissible entrance velocity of the screen in m/s, which should not be greater than 0.03 m/s; F with subscript g, the effective inflow area of the screen in m2; D with subscript g one, the outside diameter of the screen pipe of a tube well in m; L with subscript g one, the effective inflow length of the screen pipe of a tube well in m, which should be taken as 85 % of the length of the screen pipe; F with subscript g b, the inflow area of the wall of a large opening well in m2; F with subscript g d, the inflow area of the bottom of a large opening well in m2; n, the number of radial pipes of a radial well; D with subscript g two, the outside diameter of a radial pipe in m; and L with subscript g two, the inflow length of a radial pipe in m. For a water well in unconsolidated strata the design discharge shall, besides the first check, also be smaller than the permissible inflow at the bore wall, and shall be checked with a further formula. The equations themselves are printed as formulas and are not reproduced here. The text of article 4.2.4 continues beyond the pages examined.