The map of Spain where you can see how healthy the tap water in your town is

Water management in the Spanish state has several fronts: from the purely hydrological to the increasingly frequent shortage scenarios to the quality of this. Yes, the water that reaches the tap has passed through a water treatment plant and is therefore suitable for consumption, but there is a pollutant to keep an eye on: nitrates. The filtration of nutrients from the industrial agricultural activity so widespread in Spain brings about the degradation of ecosystems and also jeopardizes the security of public supply by saturating the self-cleaning capacity of aquifers and exceeding, in many cases, the treatment capacity of local water treatment plants.

Although checking the quality of the water that reaches your tap is a resource accessible to citizens through platforms such as the National Consumer Water Information System (SINAC), the reality is that sometimes databases are too technical and dense, so someone has thought of converting the information from the Ministry of Health into an interactive map that is understandable to everyone.

Is “the water of your town“and is a public consultation tool so that anyone who wants to know the quality of tap water of your municipality regarding nitrates, you can do so without needing technical knowledge through an interactive map that is easy to interpret.

The map in question has been developed by DATADISTA based on official data from SINAC, which depends on the Ministry of Health and collects the analytical results of all drinking water supply networks in Spain. It is important to highlight that the last reading dates from April 2026 and does not contain real-time measurements, but rather the frequency varies depending on the supply area. Thus, while those networks that distribute more than 10 cubic meters per day have to report, those that are smaller the report is voluntary. Hence, some small rural towns appear without data.

To make it easier, it comes with a direct search engine. Datadista

The map shows the Spanish state with an OpenStreetMap map and points distributed throughout the territory on a color scale that goes from red for those who do not comply with the regulations to green for those who comply, passing through intermediate tones for risk or surveillance situations.

In addition to being able to zoom and move the map or the Canary Islands having its own button to center the image on its archipelago, in the upper area are the layers that we can activate to view information such as the Nitrate Vulnerable Zones declared by the autonomous communities or the chemical state of the underground aquifers. In the lower left corner, the legend that explains the limits. If you prefer not to search on the map, at the top of the website there is a search box that speeds up everything and a brief summary of those critical areas.

How good (or not) is the water in your town?

Municipalities that fail to comply, critical points and control points. Datadista

At first glance, a clear correlation is obtained: the most affected areas are concentrated in areas of intensive irrigated agriculture, especially in the interior of the peninsula. If you also activate the aquifer layer, transparent white and in the bottle: there is one direct relationship between agricultural intensity and water pollution underground with which the population is supplied.

The categories in which the municipalities are classified are four:

• It fails to comply when any network registers 50 mg/L or more of nitrates, which is the parametric value set by European regulations and the Royal Decree 3/2023.
• Critical point: nitrates consistently exceed 30 mg/L. It is 60% of the legal limit and obliges the operator to develop a Water Health Plan with corrective measures.
• Control point, for those municipalities where high episodes have been detected but on a punctual and non-sustained basis.
• Complies, for municipalities that do not present a relevant risk due to nitrates.

Be careful because there are 201 municipalities and almost 91,000 people supplied within that “non-compliant” range and 885 municipalities and more than a million people who drink tap water in critical areas. It is important to consider that the final state of a municipality is always determined by the worst state of all its supply networks.

The nitrate problem. Nitrates reach the water due to the excess of nitrogen fertilizers and livestock manure, which, applied to the field (whether directly or not), are oxidized by bacterial action, transforming into nitrate, a very soluble anion that the soil does not retain and that easily infiltrates into the aquifers and rivers from which the population is supplied. The 50 mg/L limit was set by the WHO between the decades of the 50s and 60s to prevent acquired methemoglobinemia (blue baby syndrome) in infants due to high levels of nitrates in well water, the use of uncontrolled groundwater for infant formulas is not recommended.

But science has shown that the problem is more serious than that legal limit. Without going any further, a Danish study from 2018 showed that there is a greater risk of colorectal cancer from just 3.87 mg/L, the MCC-Spain project found links to aggressive prostate tumors even below that current limit. In fact, in 2025 an international group of science professionals recommended lower this safety threshold to 6 mg/L, a figure that is very far from what comes out of the taps of numerous municipalities in the state.

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