The specialists at APEM are experienced in developing and delivering water quality models to support water companies and other clients throughout the UK and Ireland. This supports them in meeting their statutory requirements with regards to the Water Framework Directive (WFD), the Water Industry National Environment Plans (WINEP) in the UK and the River Basin Management Plan in Ireland.

We have a variety of tools and methodologies to support the different requirements of our clients, from a single site through to an entire catchment. These include River Quality Planning (RQP) and Metals Permitting (MPER), and larger catchment modelling services using SIMCAT (SIMulation of CATchments) and SAGIS (Source Apportionment Geographical Information System).

Combined with our wide range of services we are able to provide a one stop shop for our clients, from survey design, water quality sampling and analysis, through data analysis and interpretation to water quality modelling solutions. This ensures consistency and quality of data and often a more cost-effective solution for our clients.

River Quality Planning (RQP)

APEM follows RQP principles to calculate the effect of a single discharge on the water quality of a river. This method helps us assess the discharge quality required to avoid an Environmental Quality Standard (EQS) failure or the discharge quality improvements needed to meet the EQS when there is a failure.

A typical usage of this tool is to determine the possible impact of an increased flow discharged at a current location, or the quality required at a given discharge to meet a specific water quality standard downstream of a new housing development.

RQP home screen. Source: Environment Agency

RQP modelling procedure. Source: Determining Uncertainty in Sediment & Nutrient Transport Models for Ecological Risk Assessment (2005). Report No 2. LWA/MDBC Project UMO43: Risk-based Approaches to Managing Contaminants in Catchments. Henderson, Brent & Bui, Elisabeth. CSIRO.

Metal Bioavailability Assessment Tool (M-BAT) and Metals Permitting (MPER)

When it comes to metal levels in water, we apply MBAT and MPER to perform similar calculations to RQP to model for metals including dissolved copper, zinc, manganese, nickel and lead. The standards for these metals are specifically based on the bioavailable fraction of the dissolved metal. This is critical for implementing the WFD and the investigations being undertaken into metal and chemical pollution in the UK and Ireland.

MPER home screen. Source: Environment Agency

Factors affecting the bioavailability of metals in water. Source: UKTAG Guide to the M-BAT.

Simulation of Catchments (SIMCAT)

The Environment Agency’s randomised water quality river model SIMCAT (Simulation of Catchments) is a crucial tool for setting and reviewing discharge permits at a catchment scale and to quantify the source apportionment of both point and diffuse pollutant load within the receiving watercourse. Driven by summary statistics of flow and quality, SIMCAT uses Monte Carlo simulation to predict in-river summary statistics for direct comparison with environmental quality standards, for example, mean concentration and 90 percentiles.

SIMCAT has been widely used for over 30 years and is recognised as being a cost-effective, practical water quality management tool to support decision making for catchment management and discharge control on a routine basis.

It provides confidence intervals for results to highlight the associated uncertainties in river and effluent flow and quality data to assist with risk-based decision making.

APEM scientists have experience of setting and reviewing discharge permits at a catchment scale with SIMCAT and have determined the source apportionment of point and diffuse pollutant loads within river catchments. This is the basis of the ‘fair share’ approach (also known as Polluter Pays Principle) in which a polluter needs to determine the improvements required to counterbalance the impact their activity has on the environment, without also being required to compensate for pollution from other sources.

SIMCAT has been used by the team of specialists for calculating the impact of discharges from sewage treatment works at a catchment scale, including the permit standards required to meet the WFD targets and the impact of closing wastewater treatment works and transferring treatment to other sites. We have also used SIMCAT models to estimate water quality impacts for drought planning studies.

Example of outputs from SIMCAT showing modelled flow and BOD concentration along a river. The vertical axis shows distance from source (Source: APEM).

SAGIS (Source Apportionment Geographical Information System) modelling

The SAGIS tool is a digital information management and visualisation platform, which serves as an integrated system for modelling water quality in rivers, bringing data to life. It provides a breakdown of chemical inputs to rivers and lakes from different contributing sectors. This enables the environmental regulators and water companies to use a common approach to develop effective solutions to improve water quality. It means that the WFD Programmes of Measures are based on sound scientific evidence and the Polluter Pays Principle.

* OSWwTW = On Site Wastewater Treatment Works (septic tanks)
Example of outputs from SAGIS showing modelled concentration of phosphate along a river and the breakdown of each contributing sector. From this, the locations of discharges from sewage works are clearly identifiable by sudden rise in the black bars. In this case the sewage works operator can see its contribution to the problem, but also that around 2 mg/l is not from its discharges and, under the fair allocation approach, it should not be responsible for this. (Source: UKWIR)

Example of source apportionment by sector from SAGIS outputs. Source: UKWIR

Example of a catchment showing the simulated concentrations of a substance at 1km intervals (blue indicates high concentrations and green low concentrations) from SAGIS outputs. Source: UKWIR

Water cycle studies

Water cycle studies help developers identify what they might need to do to ensure new developments meet the regulators’ expectations such as capacity to avoid causing environmental issues. Water cycle studies can be used by developers to help plan for sustainable growth and are especially important for infrastructure projects and the increasing demand for new housing.

CORMIX modelling

The environmental impacts of discharges into coastal water and lakes are assessed by CORMIX modelling, which demonstrates how discharges mix in the surrounding water body and at what distance environmental standards will be met. This tool is used by the APEM team to predict the mixing behaviour of discharges such as power plant cooling water, wastewater and chemicals. It has a broad range of applications relevant to large rivers, lakes or reservoirs, estuaries and coastal waters.

CORMIX 3D outputs of the modelled discharge concentration of a substance. Source

Find out how we can help you with water quality monitoring and modelling by getting in touch with Tania IglesiasSenior Aquatic Scientist.