Development and assessment of a network of water meters and rain gauges for determining the water balance. New SCADA monitoring software

Abstract

Currently the scarcity of water resources in certain areas of the Mediterranean coast, specifically in southeastern Spain, make the irrigation efficiency a vital issue when it comes to cope with the high costs of water and contribute to an environmentally-sustainable and energy-efficient agriculture.The aim of this paper is to describe the design and assessment of a system to determine the water balance of an experimental planting of four rows of eight pots of vines (Vitis vinifera L. cv Bobal). This system consisted of a network of low cost water meters and rain gauges and a supervision, control and datalogging application (SCADA) running in a compact programmable automation controller. The water meters were installed at the beginning of the rows to measure the irrigation water. Due to the low flow rate in the drainage network and given the scarcity and high price of low-flow rate flowmeters, we decided to study the feasibility of using tipping bucket rain gauges to measure the drainage water. For this reason comprehensive calibration tests were conducted to ensure their proper operation under the desired flow rate taking into account possible tilt variations in its field deployment. Data from flow meters and rain gauges were processed in the compact controller that was responsible for monitoring and generating charts in real time providing an interface accessible from the Internet. The historical data were sent to a remote FTP to have a backup and make them available from anywhere through an Internet connection. The results obtained during the system operation showed that it provided acceptable accuracy in the determination of water balance. This makes it feasible for applications such as irrigation scheduling of potted crops at a lower cost than other systems that estimate crop evapotranspiration using climatic data such as Eddy-correlation and Bowen-ratio stations.