Measuring and improving the efficiency of raw water catchments

Contents

• An increasingly demanding regulatory and environmental context
• Why assess the efficiency of raw water catchments?
• Key indicators for measuring the performance of a catchment
• Methods and tools for monitoring water catchments
• imaGeau supports local authorities in optimising their water catchments

Faced with the growing challenges of sustainable water management, local authorities and industry are questioning the efficiency of their raw water catchments, whether intended for the production of drinking water or for specific industrial uses.

Are they properly exploited? Are they sufficiently protected against point-source or diffuse pollution? This article looks at the main performance indicators that need to be monitored and how to optimise the use of water catchments without compromising the natural recharge of groundwater.

At a time when the quality of raw water from water catchments is increasingly being put to the test – in particular by frequent breaches of nitrate and pesticide standards – prevention is becoming an essential pillar. Whether the water is intended for human consumption or for industrial use, vigilance is essential at every stage. Local authorities and industry alike have a key role to play in reconciling supply performance with the sustainable preservation of resources.

An increasingly demanding regulatory and environmental context

The management of raw water resources, whether intended for the production of drinking water or for industrial use, is currently facing two pressures: on the one hand, increasingly strict regulations, and on the other, environmental conditions that are undermining the balance between abstraction and natural renewal.

Among recent regulatory developments, the PGSSE has become a key tool for local authorities. Compliance is now mandatory: by 2027 for services serving more than 50,000 people, and 2029 for those supplying more than 5,000 people. The aim is to improve the safety of drinking water by requiring systematic risk assessment throughout the production chain, from the resource to the point of distribution to the consumer.

At the same time, environmental pressures are increasing. Droughts are becoming more frequent and more intense, reducing groundwater recharge levels. Added to this is diffuse pollution, mainly from agricultural activities (nitrates, phytosanitary products), but also industrial or urban pollution, which compromises the quality of the raw water available for drinking water supply.

Against this backdrop, controlling raw water abstraction is becoming a common challenge for local authorities and industry alike. To meet regulatory constraints, guarantee a reliable supply and preserve the resource over the long term, it is essential to invest in in-depth knowledge of aquifers, step up monitoring of abstraction points and put in place strategies to prevent and anticipate qualitative and quantitative risks.

Why assess the efficiency of raw water catchments?

Regular assessment of the performance of water catchments concerns both public operators and private users of the resource. Proactive management of raw water makes it possible to anticipate deviations, optimise treatment costs and enhance security of supply – whether for human consumption or industrial use (processes, cooling, cleaning, etc.).

Integration of raw water quality monitoring

One of the cornerstones of this management system is the continuous monitoring of raw water quality, right from the point of abstraction. This makes it possible to detect pollution (diffuse or accidental), identify its potential sources (agricultural, industrial or urban), and plan appropriate corrective action. This monitoring is beneficial for :

• Local authorities are keen to keep drinking water treatment costs down;
• Manufacturers, who can avoid production stoppages or damage to installations.

Guaranteeing water that meets health standards

Providing high-quality drinking water is a key responsibility for local authorities, just as ensuring a reliable supply of raw water is a strategic issue for many industrial players. Rigorous monitoring of the efficiency of water catchments enables any deterioration in the resource to be detected quickly, emerging or chronic pollution (nitrates, pesticides, bacteria, micropollutants) to be identified, and action to be taken upstream to preserve water quality right from the point of abstraction.

Optimising water treatment costs

Non-compliant raw water can lead to additional treatment costs, interruptions in operation, even non-compliance with distribution regulations for local authorities, or risks of non-quality in sensitive industrial processes. Hence the importance of preventive management, based on detailed knowledge of the resource, regular analytical monitoring and anticipation of risk events.

Ensuring a sustainable water supply

Faced with the effects of climate change, the growing variability of rainfall events and increased pressure on underground resources, guaranteeing a sustainable supply of raw water – whether for human consumption or industrial use – is becoming a strategic imperative.

This implies the rational use of water catchments, based on rigorous monitoring of volumes abstracted, compliance with regulatory authorisations, and the ability to adjust abstractions according to the actual state of resources. For local authorities, this ensures a secure supply of drinking water. For industry, it helps to limit the risk of supply disruptions or temporary restrictions that can affect production continuity.

In both cases, dynamic and anticipatory management, based on reliable data, is essential to preserve the long-term quantitative availability of the resource and ensure the resilience of production systems.

Preserving aquatic ecosystems

Sustainable management must also take account of environmental balances. Maintaining a sufficient level in water tables and aquatic environments protects natural habitats, supports wetlands and preserves local biodiversity.

Risks associated with poor management

In addition to performance issues, inadequate management of water catchments can have serious consequences, both environmentally and financially.

Degradation of water resources

A poorly monitored or over-exploited water catchment can lead to a gradual, or even irreversible, deterioration in the quality or quantity of the resource. The appearance of pollutants, a drop in the water table or an increase in turbidity are all warning signs that should not be ignored.

Costly decontamination or abandonment of catchments

If standards are exceeded on a long-term basis, local authorities may be forced to undertake major clean-up operations, or even close down certain water catchments. This can generate significant costs, including the search for new resources, interconnections, alternative boreholes or advanced treatments. These situations undermine local autonomy in terms of supply.

Key indicators for measuring the performance of a catchment

Efficient management of raw water catchments, whether for drinking or industrial use, requires rigorous monitoring of a number of technical indicators. These data not only make it possible to check that the facilities are working properly, but also to anticipate drifts, optimise operation and secure the water supply. Here are the main indicators to monitor.

Captured volume vs. authorised volume

Monitoring the volumes withdrawn is essential to ensure compliance with prefectoral authorisations. Exceeding set thresholds can lead to administrative penalties, but above all to overexploitation of the resource, which is detrimental to its long-term survival. By regularly monitoring the flows pumped, local authorities and industry can adjust abstractions according to the season, actual needs and the state of the water table, thereby contributing to balanced management of the resource.

Overall efficiency: from catchment to tap

Overall efficiency expresses the ratio between the volume of water taken from the resource and that actually distributed to users. It is used to assess losses due to leaks in the network or unaccounted consumption (blowdowns, fires, etc.). A poor yield may mask an efficient catchment but a faulty distribution system. It is a key indicator for optimising network asset management and directing investment.

Monitoring raw water quality

Monitoring the quality of water from the point at which it is taken enables pollution to be detected upstream of the treatment chain. Nitrate, pesticide, bacterial and micropollutant levels must be analysed regularly to anticipate health risks. This monitoring is also a good indicator of the state of the catchment area, and can be used to assess the effectiveness of the protection measures put in place in the catchment areas.

Rate of availability of the resource

This indicator measures the capacity of a water catchment to supply water continuously and reliably. It takes into account interruptions caused by technical incidents, occasional pollution or restrictions imposed by the resource. A high availability rate reflects a well-maintained infrastructure and a stable resource. Conversely, a regular drop in availability may be a sign that the catchment is fragile or that there are medium-term quantitative risks.

Changes in groundwater levels and hydrological impacts

By measuring piezometric levels, it is possible to monitor changes in the groundwater being exploited. Recurring drops, particularly during the summer, may indicate overexploitation or an imbalance between abstraction and recharge. This monitoring is essential for anticipating the risk of shortages, adjusting authorised volumes and adapting operating practices in line with the hydrogeological data available.

Methods and tools for monitoring water catchments

The effectiveness of a water catchment cannot be properly assessed without appropriate measurement, control and analysis tools. The technologies available today enable precise monitoring of the resource, both in real time and over time. The combination of sensors, supervision systems and analysis platforms is an essential foundation for proactive and reactive management. Solutions such as the EMI application developed by imaGeau illustrate this move towards intelligent, integrated water management.

Metrology and instrumentation

Real-time remote management and supervision

Using historical data to anticipate and improve

By analysing the series of data collected over time, we can gain a better understanding of how the resource behaves, identify seasonal or climatic trends, and detect recurring anomalies. These elements are essential for adjusting operating practices, anticipating periods of stress, or documenting action plans as part of the SSEMP.

Solutions like EMI not only store and organise this data in a secure environment, but also automatically cross-reference it with other parameters (weather, sampling, analysis campaigns) to produce intelligent diagnoses.

imaGeau supports local authorities in optimising their water catchments

Faced with the growing challenges of drinking water safety, pressure on resources and regulatory obligations (PGSSE, protection of water catchments, sustainable management), it is essential that local authorities have the right tools to manage their water catchments proactively, based on data.

Solutions such as the EMI software developed by imaGeau enable data to be centralised, key indicators to be monitored in real time and risks relating to water quantity and quality to be anticipated. By combining instrumentation, supervision and hydrogeological expertise, they provide a comprehensive framework for enhancing the performance and resilience of drinking water supply systems.

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