Updated - 16th April 2012

At the Old School, we have a water well which is a fully brick lined 9m deep well (8m water level) which before we moved here appears not to have been used. Certainly the water that was extracted with a submersible pump was not looking the right colour for clean water !! After 5 hours of pumping, and 6000 litres later the well was nearing empty. The lining looks complete, with no falling in or precarious masonry !

The well will be used for irrigation of the garden to bring the well back into use once again. This is also the ideal opportunity to monitor the water level and report on it ! I'd hope to look at the correlation of the water level and rainfall to see how long it takes for the groundwater to permeate into the well etc.

The first step to clear the well and check that all is ok has been completed, now the designing of the sensor and water pumping equipment has been started. Based on Arduino and MQTT, the unit will be used for automation and instrumentation.

The Water Well Monitor

The water level sensor is a hydrostatic sensor from sensorsone.com, which is located at the base of the well and reports the pressure of the contained water via a current transducer. This is hooked up to an arduino which processes this data and sends an MQTT message to the hub on a 1 minute basis.

The Arduino and MQTT functionality is also used for the automatic watering part, where an MQTT message is sent from the home automation server to turn on the pump and water the garden. A home-developed algorithm has been used which takes into account the current well capacity, recent rainfall, temperatures, Evapotranspiration over the last week and forecast temps and will turn on the water flow for the correct time interval, at sun-rise and sun-set.


The Design

After deciding on a few areas to look at for this, firstly I am looking at the MPX5100DP differential pressure sensor, using one plastic tube to the bottom of the well to calculate the pressure of the column of water. For every 1m of water, 9.8kPa of pressure is produced. With a Pressure Sensor located at the top of the well, of 9m of water will give ~90kPa. From this, I can work out the water level.

The second avenue is using the IMTG from Impress Sensor Systems. This is a hydrostatic sensor which costs £226 but is highly accurate and is a current transducer. If the pressure sensor does not work out, this is the other accurate option.


Build

Arduino Nano
Arduino Ethernet Shield (Wifi later)
MPX5100DP Differential  Pressure Sensor
10m x 5mm PVC hose (Weight attached to the bottom with a U bend)

IP65 Enclosure
IP Glands