GB/T 27647-2024Technical specification for wetland ecological risk assessment (English PDF)

1 Scope

This document specifies the technical requirements for the assessment of the ecological status of a wetland, of the degree to which it is threatened, of the effectiveness of its management and of its ecological risk grade, as well as for the ecological risk analysis and monitoring of development and utilization construction projects.

This document applies to wetland ecological risk assessment, and also to the assessment of the effect of development and utilization construction projects on wetland ecological risk.

3 Terms and definitions

3.1 wetland ecological risk: the possibility that the wetland ecosystem, acted upon by an external or internal threat or carrying a potential threatening factor, undergoes a change in its ecological status that endangers the health of the wetland ecosystem. The wetland referred to in this document is the wetland as defined by the Wetland Protection Law of the People's Republic of China. Note: wetland ecological risk arises from three sides, the ecological status of the wetland itself, the extent to which the wetland is threatened and the effectiveness of wetland management. At present a development and utilization construction project is a common case of a threat to the health of a wetland ecosystem.

3.2 wetland ecological status: the state of the components, processes and services that make up the wetland ecosystem, at the corresponding scale of time and space.

3.3 natural wetland ratio: the proportion of wetland undisturbed by human activity in the total wetland area.

3.4 wetland indicator species: a biological species of a particular wetland habitat.

3.5 threatening factor to wetland: a factor that has a negative effect on, or poses a potential threat to, the health of the wetland ecosystem.

3.6 wetland vegetation suitable area: the area of wetland suitable for the growth of aquatic and hygrophilous plants and for the formation of a stable plant community.

3.7 threatening degree of wetland: the graded state that reflects the extent of change in a wetland when it is acted upon by a threat.

3.8 wetland ecological risk degree: the graded state that reflects the extent of the ecological risk of a wetland. Note: four colours, red, orange, yellow and blue, from high to low, stand for the major risk, greater risk, general risk and low risk grades of wetland ecological risk.

4 General requirements

The assessment method shall meet the following requirements. a) Quantitative and qualitative assessment are combined: the natural wetland ratio, the vegetation cover, the wetland protection ratio, the water quality and similar indicators are assessed quantitatively, while the hydrological indicators and the management effectiveness indicators other than the wetland protection ratio are assessed by qualitative description. b) The choice of assessment site, the setting out of survey lines or plots, the taking of samples and the collection of material shall follow the technical rules or standards for wetland survey and monitoring. c) In the assessment of the ecological status and of the degree of threat, one and the same indicator may be used only once within a single assessment and shall not be used again; at the same time, the omission of a key indicator, which would change the result, is to be avoided. d) An objective and impartial attitude shall run through the whole assessment, from the collection of material, remote sensing diagnosis, field survey and verification, and data processing and analysis, to the drafting of the report. e) With a view to strengthening wetland protection, this document follows in the choice of indicators, the determination of types and the determination of results the principle of taking the more severe of any two, that is, of choosing as the result the one item that gives the highest wetland ecological risk grade.

The object of assessment is the wetland patch, which is the basic unit for carrying out wetland ecological risk assessment.

For the assessment of the ecological status, the season that best reflects the indicators objectively is chosen; for the assessment of the degree of threat, the season in which the threatening factor is present or potentially present and produces a marked effect is chosen; for the assessment of management effectiveness the period is not restricted and the assessment year applies.

A reference object is chosen as needed for comparison in the assessment of the degree of threat. a) Where a time series substitution is used, a wetland in good condition at an earlier time serves as the reference, relevant material or information is collected, and the assessment year is compared with that earlier time, this being the time substitution method; the earlier time should be one of the years five or more years before the assessment year. b) Where a geographical substitution is used, a well preserved wetland of the same type nearby serves as the reference and relevant material or information is collected for a lateral comparison, this being the space substitution method. c) Where both the time substitution and the space substitution methods are used, the one giving the more severe degree of threat shall be taken as the result.

Wetland ecological risk assessment combines the three risk assessments of ecological status, degree of threat and management effectiveness. Where a wetland development and utilization construction project is involved, the content on ecological risk analysis and monitoring of construction projects is added.

5 Risk assessment of the ecological status

Assessment indicators. The indicators consist of six first-level indicators and fifteen second-level indicators, set out in Table 1. The first-level indicators are the natural wetland ratio, the vegetation cover, the coefficient of variation of the wetland indicator species and of the natural resource stock, the proportion of the area affected by harmful organisms, the hydrology and the water quality; the natural wetland ratio, the indicator species, the proportion of area affected by harmful organisms, the hydrology and the water quality are marked as mandatory indicators. The second-level indicators are the total wetland area, the natural wetland area, the wetland vegetation area and the area suitable for wetland vegetation, all in hectares and obtained by data collection, remote sensing diagnosis, field survey and verification; the number of species, the population size in head, individuals or the like per hectare, the biomass in kilograms per hectare, the standing timber volume in cubic metres per hectare, the fresh grass yield in kilograms per hectare and, for peat swamps, the thickness of the peat layer in centimetres, which is a mandatory second-level indicator for that type; the total area affected by harmful organisms during the year and the total wetland area, both in hectares; the state of water supply, the state of standing water and the state of water outflow; and the water quality of surface water, groundwater or sea water expressed as class I to class V.

Data acquisition. The data for the second-level indicators and for the water quality of the assessment year are obtained by the collection of material, remote sensing diagnosis, field survey or laboratory analysis of samples. Apart from the water quality indicator, the first-level indicators are obtained by sorting, analysing or calculating the second-level indicators. Data on harmful organisms shall be obtained in accordance with LY/T 1681 and LY/T 2516; surface water quality data in accordance with GB 3838; groundwater quality data in accordance with GB/T 14848 and HJ 164; and sea water quality data in accordance with SL 219 and GB 17378 (all parts).

Qualitative description of the hydrological indicators. The state of water supply falls into four classes: permanent supply with sufficient water, seasonal supply with sufficient water, seasonal supply with insufficient water, and intermittent supply with insufficient water. The state of standing water falls into four classes: permanent standing water, seasonal standing water, intermittent standing water and dried up. The state of water outflow falls into four classes: permanent outflow, seasonal outflow, intermittent outflow and no flow.

Calculation of the first-level indicators. The natural wetland ratio C1 is calculated by formula (1) as the total natural wetland area Sn divided by the total wetland area Ss, expressed as a percentage, both areas being in hectares. The vegetation cover C2 is calculated by formula (2) as the wetland vegetation cover area Pn divided by the area suitable for wetland vegetation Ps, expressed as a percentage. The proportion of area affected by harmful organisms C3 is calculated by formula (3) as the total area of the wetland actually affected by harmful organisms during the year Qn divided by the total wetland area Qs, expressed as a percentage. The coefficient of variation of the wetland indicator species and of the natural resource stock C4 is calculated by formulas (4) to (6) as the standard deviation Sd divided by the mean Ms, expressed as a percentage, where one of the second-level indicators is chosen as the assessment indicator and Sd and Ms are the standard deviation and the mean of the measured values Mi of that indicator, whether the number of species, the population size, the biomass, the standing timber volume, the fresh grass yield or the thickness of the peat layer, over a sample of size n not smaller than 3.

Grading. From the results of the calculation the first-level indicators are graded as excellent, good, fair or poor, the ranges of value or the qualitative descriptions being given in Table 2. The natural wetland ratio is excellent at not less than 95 %, good from 90 % to below 95 %, fair from 60 % to below 90 % and poor below 60 %. The vegetation cover is excellent at not less than 90 %, good from 80 % to below 90 %, fair from 70 % to below 80 % and poor below 70 %. The proportion of area affected by harmful organisms is excellent at not more than 10 %, good above 10 % up to 20 %, fair above 20 % up to 30 % and poor above 30 %. The coefficient of variation is excellent at not more than 20 %, good above 20 % up to 40 %, fair above 40 % up to 60 % and poor above 60 %. Hydrology is excellent with permanent water supply, standing water and outflow, sufficient water and stable hydrological features; good with seasonal supply, standing water or outflow, sufficient water and fairly stable features; fair with seasonal supply, standing water or outflow, insufficient water or some features changed; and poor with intermittent supply, standing water or outflow, drying up or no flow, and features basically changed. Water quality is excellent for surface water and groundwater of class I or II and sea water of the first class, good for surface water and groundwater of class III and sea water of the second class, fair for class IV and sea water of the third class, and poor for class V and sea water of the fourth class.

Determination of the result. From the ranges of value or the qualitative descriptions of the first-level indicators in Table 2, the grade is determined in the following order: a) if the lowest grade among the six first-level indicators is poor, the assessment grade is poor; b) if the lowest grade is fair, the assessment grade is fair; c) if the lowest grade is good, the assessment grade is good; d) if all six first-level indicators are graded excellent, the assessment grade is excellent.

6 Risk assessment of the degree of threat

Types of threatening factor. Table 3 lists nine types. Pollution covers sources of gas, solid waste and water pollution that cause the quality of the surface water, groundwater or sea water of the wetland to fall or worsen; where solid waste causes no evident water pollution but occupies wetland area, it belongs to type 3, occupation. Reclamation covers the building of dykes and dams within a wetland to form enclosures or ponds, causing fragmentation of the wetland patch or the turning of natural into artificial wetland. Occupation covers urban and rural construction, infrastructure and temporary occupation other than that needed to safeguard flood control, which turn wetland into non-wetland and reduce the natural wetland area. Human hydrological disturbance covers the interception of the water reaching the wetland, drainage of the wetland and other human activities that disturb the hydrological process and leave the wetland dry, dried up or without flow. Natural hydrological change covers precipitation, insufficient inflow from upstream or a fall in the groundwater table which have the same effect. Sediment deposition covers the gradual settling of sediment particles in the inflow, which reduces the area or the volume of the wetland. Over-utilization covers overgrazing, over-hunting or over-fishing, over-collecting, over-digging, over-felling or the excessive taking of wetland resources, which reduce the populations of wild species, the vegetation cover or vegetation area of the wetland, or the corresponding natural resource stock. Biological harm covers alien harmful organisms, whether plant, animal or micro-organism, that occupy or replace the native species of the wetland, and harmful organisms such as pests and diseases, or epidemic sources, whose occurrence kills native species, lowers their populations or reduces vegetation cover. The ninth type is any other factor that gives rise to ecological risk in the wetland.

The assessment indicators for the threatening factors are given in Figure 1. In the course of the assessment, a field pre-survey of the types of threatening factor present is first carried out, a one-to-one correspondence between the threatening factors and the indicators is established, and the types of threatening factor affecting the wetland are distinguished and determined. Where several threatening factors act on the wetland at the same time, the dominant factor shall be determined. The reference object is determined according to 4.4 and the data for the relevant indicators of the reference object are obtained by the method of 5.2.

Assessment method. a) Pollution uses the water quality indicator and biological harm may use the proportion of area affected by harmful organisms; these two indicators can be used directly to express the degree of threat. b) The hydrological indicator expresses the degree of threat by the qualitative description of Table 2 according to the state of water supply, of standing water and of water outflow. c) The natural wetland ratio is obtained from the second-level indicators of Table 1 and formula (1), the vegetation cover from formula (2) and the proportion of area affected by harmful organisms from formula (3). d) The natural wetland ratio, the vegetation cover and the second-level indicators of the wetland indicator species and the natural resource stock then give the degree of threat through formula (7). e) Apart from the pollution factor, each threatening factor may take only one of the first-level indicators listed in Figure 1 to express the degree of threat.

Calculation and grading. The degree of threat P is calculated by formula (7) as the indicator of the reference object minus the indicator of the object assessed, divided by the indicator of the reference object, expressed as a percentage, the units of the two indicators being those of Table 1. The degree of threat is graded as safe, slight, moderate or severe, as shown in Figure 2. Where the indicator of the object assessed equals that of the reference object, the threatening factor poses no threat to the object assessed and the degree of threat is recorded as safe; where the indicator of the object assessed is lower than that of the reference object, the threatening factor poses a threat and the degree of threat is graded according to the ranges of value given in Figure 2.

Determination of the result. From the grading of the threatening factors in Figure 2, the result is determined in the following order: a) if the lowest grade among the threatening factors is severe, the assessment grade is severe; b) if the lowest grade is moderate, the assessment grade is moderate; c) if the lowest grade is slight, the assessment grade is slight; d) if all the threatening factors are graded safe, the assessment grade is safe.

7 Risk assessment of management effectiveness

Assessment indicators. There are five: the wetland protection ratio, the negative list, the management body and staff, the facilities and equipment for protection and monitoring, and the protection, law enforcement, publicity, education and monitoring actually carried out.

Data acquisition. Information is collected from the forestry and grassland administration of the place where the object assessed lies: the protected area of wetland, the negative list of items required to be rectified under environmental protection inspection or the Green Shield action, the management body and staff, the facilities and equipment for protection and monitoring, and the protection, law enforcement, publicity, education and monitoring carried out. The protected area of wetland is determined in accordance with Table A.46 of the Technical Rules for the National Comprehensive Monitoring of Forest and Grassland Ecology.

Calculation and grading. The wetland protection ratio C5 is calculated by formula (8) as the protected wetland area Sp divided by the total wetland area St, expressed as a percentage, both areas being in hectares. Management effectiveness is graded as excellent, good, fair or poor. The wetland protection ratio is excellent at not less than 55 %, good from 52 % to below 55 %, fair from 45 % to below 52 % and poor below 45 %. For the negative list, excellent means no negative list, good a negative list all of whose items have been fully rectified, fair a negative list with individual items not rectified, and poor a negative list with several items not rectified. For the management body and staff, excellent means a body with full-time protection and scientific monitoring staff on the establishment, good a body with protection staff on the establishment, fair hired or temporary protection staff, and poor none. For the facilities and equipment, excellent means complete, advanced and specialized protection and monitoring stations and equipment, good stations and equipment able to maintain the present state of management, fair stations and equipment that are ageing, and poor none. For protection, law enforcement, publicity, education and monitoring, excellent means that they are carried out regularly and to good effect, good that they are carried out regularly but to ordinary effect, fair that some of them are carried out, and poor none.

Determination of the result. From the ranges of value or the qualitative descriptions of Table 4, the result is determined in the following order: a) if the lowest grade among the five indicators is poor, the assessment grade is poor; b) if the lowest grade is fair, the assessment grade is fair; c) if the lowest grade is good, the assessment grade is good; d) if all five indicators are graded excellent, the assessment grade is excellent.

8 Ecological risk assessment

According to Table 5, the results of the assessments of ecological status, degree of threat and management effectiveness are combined and the grade determined in the following order: a) if the lowest grade among the three types is red, the assessment grade is red; b) if the lowest grade is orange, the assessment grade is orange; c) if the lowest grade is yellow, the assessment grade is yellow; d) if all three types are graded blue, the assessment grade is blue.

In Table 5, blue stands for low risk, yellow for general risk, orange for greater risk and red for major risk. An ecological status assessment of excellent, good, fair or poor corresponds respectively to blue, yellow, orange and red; a degree of threat assessment of safe, slight, moderate or severe corresponds respectively to blue, yellow, orange and red; and a management effectiveness assessment of excellent, good, fair or poor corresponds respectively to blue, yellow, orange and red.

9 Ecological risk analysis and monitoring of construction projects

Basic requirements. A development and utilization construction project includes the main works, the auxiliary works, the supporting works, the public works and the temporary works, together with the resettlement brought about by the works and the works relocated, rebuilt or newly built because they are affected by the project. According to the types of threatening factor of Table 3, a development and utilization construction project within or around a wetland may pollute, reclaim or occupy the wetland or disturb its hydrology and so endanger the health of the wetland ecosystem; for that reason, content on the ecological risk analysis and monitoring of construction projects is added to the wetland ecological risk assessment.

Ecological risk analysis, for a project not yet begun but already designed or being designed, comprises the following. a) Collection of material: the planning report, feasibility study report, project proposal and other material are collected, and the type of works, the layout, the scale, the land taken, the construction technique, the production process, the resource consumption and the operating regime are determined. b) Assessment of the scheme: the engineering design scheme and the alternative schemes are assessed and compared, and, taking economic and technical feasibility into account, a recommended scheme is identified from the point of view of maintaining the health of the wetland ecosystem. c) Risk analysis: the ecological risk grade for the wetland is analysed from the land taken by the project, the construction technique, the construction operations, the construction machinery, the engineering materials, the construction waste, the daily life of the construction workers and the resettlement. d) Risk prediction: during construction, the probability of the wetland ecological risk arising, its possible causes and the source, manner, nature, extent, degree and duration of the risk are predicted; during operation, the ecological risk grade is predicted from the activities, extent, intensity and resource consumption of the project once in service. e) Where several construction projects lie within the same object of assessment, the cumulative effect on wetland ecological risk is taken into account. f) Handling of the result: for a project assessed as blue or yellow, the report shall recommend preventive measures and the drawing up of a contingency plan for wetland ecological risk; for a project assessed as orange or red, the report shall recommend that the project be stopped.

Ecological risk monitoring, for a project under construction or already in service, comprises the following. a) Period: for the construction phase, monitoring and assessment cover the whole construction process; for the operating phase, they continue until the second-level indicators of the wetland ecological status no longer change or change to a negligible degree. b) Frequency: determined by the nature, type, layout and scale of the project, monitoring should be carried out once each quarter or each half year during construction and once each half year or each year during operation. c) Indicators: the first-level and second-level indicators of wetland ecological status listed in Table 1 are used, and a prediction model is recommended for predicting the effect of the project on those indicators, so as to make the result more reliable. d) Data are obtained in accordance with 5.2. e) Handling of the result: where the wetland ecological risk grade is found to be moving from low to high, or tending that way, the report shall, for the construction phase, recommend that construction be stopped at once and put forward remedial measures, rectification and the redrawing of the design scheme, and, for the operating phase, recommend that emergency remedial measures and rectification be started at once.

10 Assessment report

The assessment report is mainly in words, and figures, tables and words may be combined; it covers the object of assessment, the assessment method, the assessment result, and the conclusions and recommendations. The outline of the report is given in Annex A.