Danestream, Milford-on-Sea: When the River Tells a Different Story

As part of New Forest Water Watch’s late May weekend of monitoring, Danestream Dippers carried out yet more tests on the stream at Milford-on-Sea. It was immediately obvious that a serious pollution event had taken place somewhere upstream and they responded quickly. What began as concern quickly escalated into a clear pollution incident, one that highlights both the value and the necessity of careful, local environmental monitoring.

Warning signs

We already had the evidence of dangerously high E. coli levels in the river (91 000 CFU/100ml), but alongside this, the first indicators were physical: the river was grey-brown and stank. The second indicators were biological.

Fish were observed gasping at the surface, behaviour typically associated with severe environmental stress, most commonly low dissolved oxygen or acute pollution exposure. As we moved along the stream, it became clear that conditions were deteriorating. Grey filamentous strands of sewage fungus became abundant. Aquatic life appeared to be disappearing; where were the invertebrates? We had long ago observed an absence of plant life in the stream. Small fish were seen gasping in oxygen-depleted water; dead fish were then found.

These are not subtle signals. They are immediate and serious indicators that something is wrong. Together, these indicators are consistent with acute organic pollution and severe oxygen depletion.

Sampling and investigation

In response, we raised our game; sampling, measuring, and recording environmental data. We took temperature, ammonia, nitrate and phosphate readings. Measurement of ammonia is cheaper for us than the E. coli tests we had been carrying out as an environmental indicator. However, point measurements alone rarely tell the full story in dynamic systems like small streams.

Crucially, we continued further upstream.

This step, physically tracing the watercourse, bridged the gap between suspicion and confirmation. The Danestream Dippers had informed the Environment Agency of high levels of E. coli weeks ago. Southern Water were sent in and we were told that there was no issue. The biological evidence strongly suggested otherwise. We made another phone call to the emergency line at the Environment Agency. When we saw children playing on rope swings over the stream, we urged them to get out of the water.

Identifying the source

We work alongside Adam Ellis of FLOW CIC and we are hugely grateful for him taking the next step. Donning chest high waders, he entered the stream to investigate directly. Guided by smell, river appearance and physico-chemical indicators, he was quickly able to identify the source of the problem.

An outlet was located.

At this point, the situation moved from uncertainty to confirmation: a pollution event was actively occurring.

Response

Following identification of the source, a significant response was initiated. A third incident was reported to the Environment Agency. With some difficulty, they found the site.

Personnel from both the Environment Agency and Southern Water attended the site; pumps were shut down and tankers were deployed to remove contaminated flows.

This level of response indicates the seriousness of the incident and the importance of rapid intervention once a source is confirmed.

Why this matters

This incident demonstrates several important points.

First, biological observation remains one of the most sensitive indicators of environmental change. Fish gasping at the surface provided an early and unambiguous signal that conditions were deteriorating.

Second, New Forest Water Watch monitoring groups such as the Danestream Dippers play a critical role in identifying issues that may not be immediately detected through routine or remote assessment. Localised discharges can be easily missed without on-the-ground presence.

Third, persistence matters. Initial reassurance, and even denial, from Southern Water did not reflect the conditions observed in the stream. Continuing to investigate, guided by evidence rather than assumption, was key to identifying the problem.

Moving forward

While it is encouraging to see a rapid overnight response once the issue was finally confirmed, that confirmation from the authorities took too long. We first reported this weeks ago. We were victims of doubt and disbelief and now important questions remain:

• What was the exact nature of the discharge?

• How long had it been occurring?

• What ecological impact has it had?

• What measures will be implemented to prevent recurrence?

• Will the Environment Agency or Southern Water undertake regular monitoring of the Danestream?

We will be seeking clarity on these points, and we ask the parish council to seek similar answers.

Conclusion

This was a case where the river itself provided the first and most reliable warning.

By listening to those signals, and acting on them, we were able to help bring about intervention.

This is why monitoring matters. It’s why local knowledge matters. And this is why we continue.