Evapotranspiration (ET) is a fundamental component of the hydrological cycle. Accurate estimation of ET is crucial for water balance calculations, the design and management of irrigation and drainage systems, and overall water resource planning.
This repository contains the hardware designs, circuit diagrams, and Arduino firmware for building a highly precise, low-cost Automated Micro-Lysimeter. The system utilizes a gravimetric approach based on water balance equations to directly measure reference evapotranspiration (
Lysimeters are widely recognized as one of the most reliable instruments for the direct measurement of evapotranspiration. This project employs a weighing micro-lysimeter mechanism. By continuously monitoring the mass of an isolated volume of soil and vegetation, the system detects minute weight changes corresponding to water loss via evaporation from the soil and transpiration from the crop.
To ensure the measured values accurately represent reference evapotranspiration (
- Crop Type: Grass reference crop.
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Seeding Density: 70-90
$g/m^2$ distributed uniformly. - Height Management: Initial measurements commenced when the grass reached 12 cm. The height was strictly maintained between 10 cm and 15 cm throughout the evaluation period (Allen et al., 1998; Rahimikhoob et al., 2020).
- Soil Moisture: To avoid any water stress that could limit transpiration, soil moisture was constantly monitored and maintained at Field Capacity (FC).
The hardware consists of a robust iron frame equipped with four 50 kg load cells, providing a cumulative capacity of 200 kg.
- Microcontroller: Arduino UNO R3 (DIP)
- Sensing: 4x Load Cells + HX711 24-bit ADC
- Timekeeping: DS3231 Real-Time Clock (RTC)
- Data Storage: Micro SD Card Module (YS-41)
- Display: 16x2 Character LCD
(For complete wiring and assembly instructions, please refer to the Hardware/ and Documentation/ folders.)
| Directory / File | Description |
|---|---|
📁 Arduino/ |
Main .ino firmware for data logging and HX711 integration. |
📁 Hardware/ |
Circuit diagrams, pinout guides, and mechanical components list. |
📁 Calibration/ |
Standard protocol and results for load cell calibration. |
📁 Example_Data/ |
Sample dataset (85-hour continuous ET measurement). |
📁 Figures/ |
System photos, 3D printed parts, and weight change graphs. |
📁 Documentation/ |
Comprehensive User_manual.md for assembly and operation. |
📄 CITATION.cff |
Citation details for referencing this project in academic papers. |
To replicate this setup:
- Review the Components List and acquire the necessary hardware.
- Follow the Circuit Wiring Guide to assemble the electronics.
- Perform the calibration procedure outlined in Calibration Protocol.
- Read the User Manual for detailed instructions on software installation and agronomic preparation.
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Allen, R. G., Pereira, L. S., Raes, D., Smith, M., & others. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. Fao, Rome, 300(9), D05109.
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Blankenau, P. A., Kilic, A., & Allen, R. (2020). An evaluation of gridded weather data sets for the purpose of estimating reference evapotranspiration in the United States. Agricultural Water Management, 242. https://doi.org/10.1016/J.AGWAT.2020.106376
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Rahimikhoob, H., Sohrabi, T., & Delshad, M. (2020). Assessment of reference evapotranspiration estimation methods in controlled greenhouse conditions. Irrigation Science, 38(4), 389–400. https://doi.org/10.1007/s00271-020-00680-5
Developed for academic research and greenhouse water management at the University of Tehran by Morteza Khoshsimaie Chenar, Ph.D. in Irrigation and Drainage Engineering