Must-Read: Tom Friedman On Climate Change And ‘The Other Arab Spring’
NOAA concluded in 2011 that “human-caused climate change [is now] a major factor in more frequent Mediterranean droughts.” Reds and oranges highlight lands around the Mediterranean that experienced significantly drier winters during 1971-2010 than the comparison period of 1902-2010.
There are various approaches for scheduling irrigation. One approach is to supplement rainfall with enough irrigation so that the cumulative rainfall and irrigation, over a specific period of time (e.g., one day, one week, one season), matches the estimated crop water requirement.
The information on this page will allow you to schedule your irrigation in this manner. Here is how it works:
1. First, and this is the hardest part, create an evapotranspiration crop coefficient (Kc) curve for your crop. The following link to the Food and Agriculture Organization (FAO) Document No. 56 provides guidance on the construction of a Kc curve: CLICK HERE. Your Kc curve should look like FAO 56 Figure no. 34 when you are finished. (FYI: Crop coeffiecient curves can also be created using the PRET computer program)
2. Now it gets easier. Go to the appropriate reference evapotranspion (ETo) map(s) for Puerto Rico and determine the ETo for your location CLICK HERE. Note, if you are irrigating ever day, then you only need to obtain the ETo for yesterday’s date. If, however, you are irrigating once per week, for example, then you will need to get the ETo values from the maps for the previous week. In this latter example, you will need to sum the daily values of ETo to obtain a value of the weekly ETo.
3. From your Kc curve, determine a representative value of Kc for the time period of your analysis (e.g., daily or weekly).
4. Estimate the crop water requirement (crop evapotranspiration) ETc = Kc x ETo.
5. Estimatate the required depth of irrigation: Irrigation = ET – Rainfall. If the estimated Irrigation is negative, then you do not need to irrigate.
It is recommended that you measure the rainfall on your farm with a rain gauge, however, if you do not have access to the measured rainfall, you can obtain an estimate of the rainfall (derived from NEXRAD radar) by clicking here.
The irrigation scheduling approach described above is based on various simplifying assumptions (e.g., surface runoff and deep percolation are ignored). Nevertheless, it will vastly improve your water management if you are not currently using an irrigation scheduling method. To evaluate your irrigation management, you may want to construct a graph similar to the example provided below. The graph shows the cumalative depth of irrigation and ETc plotted with time. If these two curves stay close together then you are doing a pretty good job of managing your irrigation.
Example of the cumulative irrigation and ET plotted with time for a crop season. The goal of irrigation scheduling is to try to match the applied irrigation with the ET. By the end of the season, the cumulative irrigation should more or less equal the cumulative ET.
The methods used to obtain ETo and rainfall can be obtained at the following website: GOES-Puerto Rico Water and Energy Balance (GOES-WEB) Algorithm
For another method of irrigation scheduling that takes into account soil moisture, see A simple Irrigation Scheduling Spreadsheet Program
DISCLAIMER: The information is provided “as is”. The authors and publishers of this information disclaim any loss or liability, either directly or indirectly as a consequence of applying the information provided herein, or in regard to the use and application of said information. No guarantee is given, either expressed or implied, in regard to the accuracy, or acceptability of the information.
GOES-PRWEB is finally operational. 
I would like to thank my student, Victor Reventos, who made it possible through his Python programming skills. Here is a link to the results:
http://academic.uprm.edu/hdc/GOES-PRWEB_RESULTS/
New results will be published daily. Historical results are available from January 1, 2010. A list of the available output is provided below.
For information on GOES-PRWEB please visit the following link:
https://pragwater.com/goes-puerto-rico-water-and-energy-balance-goes-web-algorithm/
Eric Harmsen
GOES-PRWEB RESULTS
NON-TRANSIENT PARAMETERS
ACKNOWLEDGEMENTS: This research received partial funding from the following sources: NOAA-CREST (grant NA06OAR4810162) and USDA Hatch Project (Hatch-402). Special thanks to Dr. John Mecikalski for providing the solar radiation data, and Alejandra Rojas for providing various GIS maps used in this research.
DISCLAIMER: The information is provided “as is”. The authors and publishers of this information disclaim any loss or liability, either directly or indirectly as a consequence of applying the information provided herein, or in regard to the use and application of said information. No guarantee is given, either expressed or implied, in regard to the accuracy, or acceptability of the information.
Dear Friends
Total estimated actual evapotranspiration for 2010 derived from the GOES-PRWEB algorithm.
I am sending out this “heads up” to let you know that within the next few days the GOES-Puerto Rico Water and Energy Balance (PRWEB) model will become operational. “Operational” means that the results will appear on the website everyday. The water and energy balance results, and all other environmental parameters will be published in “near real-time” (i.e., through yesterday’s date). In other words, if you visit the website on April 2, 2012, for example, the results will be current up through April 1, 2012. In addition, graphic results will be provided on a daily basis starting from January 1, 2010.
As always, feel free to respond to my posts with questions or comments.
Eric
Can we solve global water scarcity?
This is a great article!
Management of Drip/Trickle or Micro Irrigation
By Megh R. Goyal, PhD, Professor in Agricultural and Biomedical Engineering, University of Puerto Rico
http://www.appleacademicpress.com
This important book—the only complete, one-stop manual on microirrigation worldwide—offers knowledge and techniques necessary to develop and manage a drip/trickle or micro irrigation system. The simplicity of the contents facilitates a technician to develop an effective micro irrigation system. Management of Drip/Trickle or Micro Irrigation includes the basic considerations relating to soil-water-plant interactions, with topics such as methods for soil moisture measurement; evapotranspiration; irrigation systems; tensiometer use and installation; principles of drip/ micro/trickle irrigation; filtration systems; automation; chloration; service and maintenance; design of drip irrigation and lateral lines; the evaluation of uniformity of application; and an economical analysis for selecting irrigation technology.
CROP WATER USE ( HARGREAVES ET EQUATION) NEW WOLFRAM ALPHA WIDGET. Reference: Hargreaves, G. H. and Z. A. Samani, Reference Crop Evapotranspiration from Temperature. Appl. Eng. Agric., ASAE. 1(2). 1985,. pp.96-99.
Widget Application: Suppose you want to schedule irrigation by replacing the water evapotranspired by your crop each day. 1. Click on the appropriate link to get yesterdays solar radiation for your location: Puerto Rico or Northern Caribbean, 2. Check the internet for the average daily air temperature at your location (average = (minimum + maximum)/2), 3. Get the appropriate crop coefficient for your crop from this link, and 4. Finally, enter solar radiation, air temperature and crop coefficient into the widget to estimate ET. Multiply ET x acres x 1069.0663 to get the number of gallons of water you need to apply to your field.
Rescued Meteorological Data for the Caribbean Region – Excellent Historical Resource
These data are stored in NOAA’s digital library under the heading: Data Rescue Caribbean. Many of the recorded measurements are from the first half of the 20th Century.
For other interesting historical NOAA documents, check out the following link: http://docs.lib.noaa.gov/rescue/
PRAGWATER 
