Lead Investigators:

Thomas Harmon (UC Merced), Jose Saez (Loyola Marymount University)

Overview

Automatic irrigation control system has been designed to monitor nitrate in groundwater in Merced backyard and Palmdale, CA. The main objective of automatic control setup in Merced backyard is to test feedback control theory using off-the-shelf automatic flow controller and data acquisition system for the deployment of wireless sensor network system in Palmdale, CA to observe and control nitrate transport in agricultural soils when the nitrate-laden reclaimed water is used for irrigation.

Figure 1. Automatic irrigation control system in Merced backyard

Approach

Receding Horizon Control (RHC) theory for automatic irrigation control is implemented in support of vertical array of soil sensor data, weather station data, process simulation models, and optimization schemes. A data acquisition system interfaces a computer with automatic flow controller and sensors. On-line observations are used to update simulation models and optimization schemes provide the system with optimal irrigation rate through automatic flow controller to supply the exact amount of water needed.

Systems/Experiments

A test bed automatic irrigation system is composed of a flow controller (LCR-5LPM-D, Alicat Scientific Inc., Tucson, Arizona), a data acquisition system (NI DAQcard-6024E for PCMCIA, National Instruments, Austin, Texas), soil moisture sensors (EC-10, Decagon Devices, Pullman, Washington), soil temperature probes (TMCx-HD, Onset Computer Corp., Bourne, Massachusetts), nitrate ion selective electrodes (Sentek, Essex, UK), and a weather station (Vantage Pro2, Davis Instruments, San Francisco CA).

Sensors are installed at different depths; temperature sensors at 10, 20, 40 cm, soil moisture and nitrate sensors at 10, 20, 40, 60cm to investigate one dimensional profile of soil moisture, temperature, and nitrate transport. An automatic flow controller is a device capable of positioning the valve according to the optimal flow rate by accepting analog signal from a computer. A bucket of water with known quantity of nitrate concentration is sprinkled to the site using this flow controller. A flow controller, a data acquisition system, sensor data, and a computer are interconnected in a closed-loop to automatically control irrigation.

Future Directions

The RHFC system has been fabricated and is currently being installed at the Merced backyard test bed.  The system will be tested in a series of experiments aimed at optimizing irrigation using reclaimed wastewater.

People

Faculty:

• Thomas C. Harmon (UC Merced Engineering)
• Jose Saez (Loyola Marymount Civil & Environmental Engineering)

Researchers:

• Alexander A. Rat'ko (UC Merced Environmental Systems)

Graduate Students:

• Yeonjeong Park (UCLA Civil & Environmental Engineering)

Undergraduates:

• Chris Butler (UC Merced Environmental Engineering)