7.10 Subprogramme RW: Runoff water chemistry

• 7.10.1. Introduction
• 7.10.2 Methods
• 7.10.2.1 Discharge measurements
• 7.10.2.2 Water chemistry sampling
• 7.10.2.3 Handling of water chemistry samples
• 7.10.3 Analytical techniques
• 7.10.4 Quality assurance/Quality control
• 7.10.5 Data reporting
• 7.10.6 References

7.10.1. Introduction

Runoff is the main output of solutes from a catchment area. The amount of element loss can be calculated by measuring the runoff and analysing the concentrations of runoff water.

The parameters included on the mandatory list are, with few exceptions, those also mandatory in the ICP Waters programme and mainly related to acidification. The optional determinants are also mostly those listed optional in the ICP Waters programme.

Mandatory parameters:

anions: alkalinity, sulphate, nitrate, chloride
organic: dissolved organic carbon
cations: pH, calcium, magnesium, sodium, potassium, inorganic (labile) aluminium ¹⁾
nutrients: total nitrogen, ammonium
physical properties: stream runoff, specific conductivity

¹⁾ Difference between reactive (organic + inorganic) and non-labile (organic) aluminium. May be omitted at pH>5.5.

Optional parameters:

physical properties: water temperature
nutrients: total phosphorus, soluble reactive phosphate, total sulphur, silica
metals: iron, manganese, cadmium, zinc, copper, nickel, lead, arsenic, chromium, molybdenum, total aluminium
other: fluoride, colour

7.10.2 Methods

7.10.2.1 Discharge measurements

The discharge must be determined in order to calculate catchment budgets. The best approach is to establish permanent weirs with continuous recording stage height recorders (see e.g Nord 1989:11). At least daily values of runoff should be recorded. During periods of high flow- snow melting, heavy rains, storms - discharge measurements should be carried out more frequently. Disharge should also be measured always when water chemistry samples are taken.

7.10.2.2 Water chemistry sampling

Locate the runoff chemistry sampling close to the runoff recording device. If a weir is present, sampling is done at some distance up-stream from the weir because of the risk of chemical contamination from the weir material. If no weir is present, sample in a deep flowing part of the stream at a depth sufficient to avoid sediment and surface contamination. Samples are taken with a water sampler from 10-50 cm depth. In shallow streams, where this is not possible, samples are taken in such a way that contamination and sampling of surface films is avoided. When filling the bottle, keep the bottleneck against the current, well below the surface. Rinse the bottle and screwcap 3 times with sampling water prior to sampling. Avoid touching the inside of bottle and screwcap.

If some form of automatic water sampler is used, it should be tested for contaminants, especially if heavy metals are analysed.

The aim of the sampling should be to obtain spatially and temporally representative samples. Spatial representativeness in this context refers to the pattern of variation in water chemistry across the stream cross-section. This is a function of the turbulence within the stream: the water in small streams with rocky beds and steep gradients is better mixed than water in larger, slower-moving rivers. Temporal representativeness may be particularly difficult to achieve, escpecially for small streams fed primarily by precipitation (as opposed to groundwater-fed streams). Consequently, samples should be collected at such intervals that no important cycle of change in concentration could pass unnoticed between sampling times.

Runoff water samples are taken at least once a month. However, for establishing catchment budgets a flow weighed sampling is recommended. Disharge should also be measured always when water chemistry samples are taken. The sampling integration time should if practical be harmonized with other relevant subprogrammes e.g. deposition and throughfall measurements.

7.10.2.3 Handling of water chemistry samples

Please see Chapter 8.2 for details.

7.10.3 Analytical techniques

For a list of available standards, see Chapter 8.5.

7.10.4 Quality assurance/Quality control

See data quality management in Chapter 8.

7.10.5 Data reporting

1) Please note the change of unit.

Important: if the titration is made to one single pH value (usually pH 4.5) it is necessary to indicate (using the correct determination code in DB list) whether the given value is adjusted to be the endpoint value or represents the total acid consumption to pH 4.5.

Example files

RW example Excel file
RW example ASCII file

• File identifier SUBPROG states the subprogramme.     
• MEDIUM is left blank.     
• LEVEL is given as sampling depth from the surface (cm).    
• Spatial pool SPOOL refers to the number of sampling points.     
• If sampling is carried out more than once a month, the values should always be given as flow weighted means, status flag is W, except for temperature, colour number and conductivity, which are reported as arithmetic averages for several sampling dates/month. Monthly values are reported without status. Stream runoff is reported as a monthly mean. For calculation of flow weighted means, please see Annex 7. General information on flags is given in Chapter 4. 
• Sampling year and month are given as YYYYMM, day field is left blank.

7.10.6 References

ICP Waters Programme manual. Compiled by the Programme Centre, Norwegian Institute for Water Research. Revised edition, Oslo.

Methods for Integrated Monitoring in the Nordic Countries. Miljøraport 1989:11 section 5. Nordic Council of Ministers, Copenhagen 1989.