River Eden Demostration Test Catchment river flow and nutrient time series monitoring dataset

The Demonstration Test Catchments (DTC) programme was established in December 2009 to inform the mitigation of agricultural water pollution across farmed landscapes in England. We took a "learning by doing" approach, developing, testing, and demonstrating suites of measures at landscape scale that were practical within commercial farming systems. The river catchment was adopted as the spatial unit for understanding and managing water quality, balancing the demands of food production against environmental protection. Since agricultural pollution is diffuse, sporadic, and weather-driven, assessing the effectiveness of mitigation required long-term monitoring both before and after on-farm interventions. Delivering this at catchment scale required close interaction between stakeholders, regulators, and scientists.

We monitored stream water quality and biology and examined catchment responses to storm events. Measurements included nitrogen, phosphorus, and sediment concentrations, together with the total volume of water leaving each catchment.

Turbidity. Turbidity is the reduction in the transparency of a solution caused by suspended sediment particles, coloured organic matter, and the water itself, which scatter, reflect, and attenuate incident light. It is the most widely used surrogate for suspended sediment concentration. At the sub-stations, we used McVan Analite 390 Digital Series nephelometers, which comply with ISO 7027 and operate at depths of up to 100 m. These instruments measure light scattered at 90° to the incident beam, using a near-infrared source (860 nm; spectral bandwidth ≤ 60 nm) and a path length of less than 10 cm. They measure turbidity over 0–1000 NTU with a precision of ±1%. Readings were taken at 15-minute intervals.

Automatic sampling. Each water quality monitoring station was equipped with an ISCO 3700 automatic sampler, comprising an intake, sample distributor, pump, bottle container unit, and activation system. Samples were drawn from the channel by suction, with volume determined by peristaltic pump speed and the number of pump rotations. These samplers are lightweight, affordable, and computer-controlled, and can be triggered remotely or automatically in response to rainfall or changes in river level. 

Outlet stations: multiparameter sondes. Each outlet station was equipped with a YSI 6600 V2 sonde, which simultaneously measures:

• conductivity (0–100 mS cm⁻¹, ±0.5%)
• temperature (−5 to +50 °C, ±0.15 °C)
• pH (0–14, ±0.2 units)
• dissolved oxygen (0–500%, ±2%)
• turbidity (0–1000 NTU, ±2%)
• chlorophyll-a (0–400 µg L⁻¹)

Newby and Pow outlet stations: nutrient sensors. These two stations carried additional in situ nutrient analysers:

• Ammonium: A Hach NH4D sc sensor used an ion-selective electrode (ISE) to measure ammonium (NH₄⁺) directly as NH₄-N, with a differential pH electrode as the reference for stability. Potassium (K⁺) is the main interferent, so an integrated potassium ISE was used to correct the ammonium reading. Operating range: 0.2–1000 mg L⁻¹ (±5%).
• Nitrate: A Hach Lange Nitratax sc sensor provided self-cleaning, immediate measurement of nitrate-N (NO₃-N), with turbidity compensation via a reference measurement. Operating range: 0.1–100 mg L⁻¹ (±3%).
• Phosphorus: A Phosphax sigma process photometer provided continuous measurement of total phosphorus and orthophosphate, based on the DIN-equivalent molybdenum blue method. A chemo-thermic digestion ensured complete breakdown within a few minutes. Operating range: 0.01–5.0 mg L⁻¹ for both total P and PO₄-P.