Posts Tagged: CIMIS irrigation
Water Use Where There is NO Weather Station
Spatial Overview - How it Works
The California Irrigation Management Information System (CIMIS) currently manages over 145 active weather stations throughout the state. Archived data is also available for 85 additional stations that have been disconnected from the network for various reasons. Most of the CIMIS stations produce estimates of reference evapotranspiration (ETo) for the station location and their immediate surroundings, often in agricultural areas. Because of California's diverse landmass and climate, many locations within the state lack a representative CIMIS station. Some counties, for example, do not have a CIMIS station and others have only one or two stations. As a result, there are significant spatial ETo data gaps, especially in urban areas. In an attempt to mitigate this problem, CIMIS initiated a study to investigate the possibility of coupling remotely sensed satellite data with point measurements from the CIMIS weather stations to generate spatially distributed ETo values (ETo maps).
A contract was awarded to the University of California Davis (UCD) remote sensing group, lead by Professor Susan Ustin, to conduct the study. The Department of Water Resources (DWR) formed an advisory committee comprised of individuals with expertise in remote sensing, GIS, modeling, and water management from DWR and UCD. The committee met, on an as needed basis to discuss new developments and plan future actions. After thorough research, the team decided to use combinations of data derived from satellites and interpolated from CIMIS station measurements to estimate ETo at a 2 kilometer (km) spatial resolution. The resulting product has been vigorously tested and has demonstrated a degree of accuracy that is acceptable for most irrigation applications. The CIMIS program will continue to evolve and expand to meet the future irrigation information needs of California. For a brief description of the methodology used to generate the ETo maps, see the Spatial Model discussion below.
Spatial Model
Daily reference evapotranspiration (ETo) at a 2 km spatial resolution are calculated statewide using the American Society of Civil Engineers version of the Penman-Monteith equation (ASCE-PM). Required input parameters for the ASCE-PM ETo equation are solar radiation, air temperature, relative humidity, and wind speed at two meters height. These parameters are estimated for each 2 km pixel using various methods.
Daily solar radiation is generated from the visible band of the National Oceanic and Atmospheric Administration's (NOAA) Geostationary Operational Environmental Satellite (GOES) using the Heliosat-II model. This model is designed to convert images acquired by the Meteosat satellite into maps of global (direct plus diffused) irradiation received at ground level. The model has also been used with other geostationary satellites such as the GOES. For details on the Heliosat-II model and its accuracy, please refer to the HelioClim web page.
Interpolation
Air temperature, relative humidity, and wind speed values at each pixel were obtained by interpolating point measurements from CIMIS stations. Originally two interpolation methods, Spline and DayMet, were selected based on accuracy of results, code availability, and computational efficiency. Spline – the method currently used – is an interpolation method that fits a surface through or near known points using a function with continuous derivatives. Two- or three-dimensional Spline is used based on which weather parameter is to be interpolated.
The accuracy of both methods has been tested using cross-validation analysis, but DayMet is no longer used. DayMet is an interpolation method that was developed at the University of Montana to generate daily surfaces of temperature, precipitation, humidity, and radiation over large regions of complex terrain. It determines the weights associated with a given weather station for each point where weather parameters are to be determined depending on the distance and density of the stations.
The accuracy of ETo values estimated from these methods depends on many factors. For example, solar radiation remotely sensed through GOES is significantly affected by such factors as cloudiness and snow cover. Therefore, mountainous areas with snow cover and coastal areas with cloud and fog are more susceptible to errors. Also, interpolation accuracy is affected by the density of the weather stations and geographic features of the region. CIMIS stations are purposely placed in irrigated, open, flat areas – usually valleys – to provide the best reference data for adjacent farmlands and other irrigated areas. As a result, interpolation in valleys between CIMIS stations may not provide accurate data for mountainous terrain. Despite these potential problems, however, we believe the ETo estimates provided will be superior to only using data from a distant weather station with a different microclimate. For CIMIS station Siting criteria click the “Siting” tab.
Further Details
For detailed descriptions of the methodology used to map daily ETo, refer to the RESOURCES navigation button https://cimis.water.ca.gov/Resources.aspx
If you would like to get ETo data created using the methods described here, you may do so by logging into your account, clicking on the SPATIAL navigation bar, then on the Spatial Report tab. If you do not have a CIMIS account, you can create one by registering with us. Please note that CIMIS data is provided free of charge and registration is required for statistical purposes only. https://cimis.water.ca.gov/Default.aspx
satellite weather station
Forecasting Crop Water Use?
The California Irrigation Management Information System (CIMIS) is a program unit in the Water Use and Efficiency Branch, Division of Regional Assistance, California Department of Water Resources (DWR) that manages a network of over 145 automated weather stations in California. CIMIS was developed in 1982 by DWR and the University of California, Davis (UC Davis). It was designed to assist irrigators in managing their water resources more efficiently. Efficient use of water resources benefits Californians by saving water, energy, and money. https://cimis.water.ca.gov/
CIMIS reflects the energy that has arrived to drive water use by crops. It is the past. Now the National Weather Service has devised a way of forecasting water use, so that growers can be better prepared for irrigation. The question is how well does this new system work. Well, here are the results or a study that should lend confidence in the predictive value of the system.
COMPARISON BETWEEN FORECASTS OF REFERENCE EVAPOTRANSPIRATION and ETo VALUES CALCULATED USING DATA FROM DIFFERENT CLIMATIC CONDITIONS.
G. Ben Hamouda, F. Ventura, D. Zaccaria, R.L. Snyder, K.M. Bali.
Evapotranspiration is the transfer of water from the earth's surface to the atmosphere. It comprises the sum of water losses to atmosphere due to the processes of evaporation of moisture from soil, water bodies and wet plant canopies, and the transpiration of water from plants. Forecasts of this crucial component of the hydrologic cycle can be very valuable for growers, farm managers, irrigation practitioners, water resource planners and managers, and reservoir operators for their planning, allocation, delivery and scheduling decisions, as well as to hydrologic scientists for research purposes. Verifying the reliability of models' forecasts is among the critical tasks for development and performance evaluation of physical models. In fact, the verification allows understanding the models' behavior under different climatic conditions, and evaluating their applicability and dependability.
The US National Weather Service (NWS) has released a product that provides forecasts of reference evapotranspiration (FRET) at 2.5-km grid resolution for the entire continental US. In this study, a comparison is made between ETo estimates from FRET and ETo values calculated by the California Irrigation Management Information System (CIMIS) for 68 days during summer 2019. Both the FRET forecasts and ETo values were obtained from NWS and CIMIS, respectively, on the basis of 15 CIMIS locations that are representative of different climatic conditions in California. In addition, air temperature, dew point temperature, relative humidity, wind speed, and vapor pressure deficit (VPD) data were also collected/calculated from the NWS and CIMIS websites to analyze the sensitivity of FRET forecasts to predictions of these parameters. All FRET forecasts were performed with timescales of 1, 3, 5 and 7 days. Statistical indices were calculated to assess the dependability of FRET values. They showed a good correlation of the FRET model outputs with CIMIS ETo data, with some differences depending on the climatic characteristics of selected weather stations' locations, suggesting that FRET data could be valuable for anticipating near-future water demand and improve irrigation management in California.
Look for a more detailed description of this study in a forthcoming edition of the Journal of Irrigation and Drainage Engineering – ‘Evaluation of Forecast Reference Evapotranspiration (FRET) for Different Microclimates Regions in California to Enable Prospective Irrigation Scheduling' - https://ascelibrary.org/journal/jidedh
FRET is available at:
https://www.weather.gov/abr/etforecasts
And more:
https://www.weather.gov/cae/fretinfo.html
https://www.weather.gov/abr/etforecasts
https://ui.adsabs.harvard.edu/abs/2016AGUFM.H21D1430O/abstract
https://www.weather.gov/ict/Evapotranspiration
Teachers observe next generation science in action on Kearney tour.
Third grade teachers from around California toured UC ANR Kearney Agricultural Research and Extension Center (KARE) Center July 21 during a week of Next Generation Science Standards training in nearby Reedley sponsored by the K-12 Academy and WestEd.
Led by Chuck Boldwyn, KARE superintendent of agriculture, tour stops highlighted the California Irrigation Management Information System (CIMIS) weather station, sorghum deficit irrigation trials, and how a soil weighing lysimeter measures tree and vine crops water use.
Boldwyn encouraged teachers to subscribe to California Agriculture journal. Readers in the United States can subscribe for free. Published by the UC Division of Agriculture and Natural Resources (ANR), the quarterly peer-reviewed journal reports on research, reviews and news of California's agricultural, natural and human resources. Content can be easily understood by non-specialist readers. International subscription rates are $24 a year, or $20 a year for two years or more.
Khaled Bali, UC Cooperative Extension specialist in statewide irrigation water management at KARE, explained at the weather station how the data is used for irrigation management decisions. CIMIS was developed in 1982 by the California Department of Water Resources and UC Davis. One of the first CIMIS weather stations to be put into use is still located at the UC ANR West Side Research and Extension Center in Five Points.
At a stop in a peach orchard, teachers were surprised to learn of the large weighing lysimeter just below their feet. Basically, a lysimeter is a large "flower pot" measuring 6.5 feet wide by 13 feet long by 6.5 feet deep that rests on a sensitive balance-beam weighing scale in an underground chamber. Why would you want to measure soil weight? Short-term soil weight loss is almost entirely due to water evaporation through leaves or from the soil surface. When a specific threshold is exceeded, the crop is automatically irrigated. The orchard lysimeter has also been used to study the effects of water stress on tree water use. Two lysimeters were constructed at KARE in 1986. The second lysimeter is located in a vineyard.
Comments from teachers recognized the value of the agricultural science research underway at KARE.
"I was not aware of all the research that is going on in ag."
"A great tour. I hope the Reedley teachers take advantage of having the Kearney Center so close to them."
"It was amazing to see the concepts we have been learning put to work."
Estimated Crop Coefficients for Strawberry
Several strawberry growers have expressed interest in using evapotranspiration data for scheduling irrigations in strawberries, especially during the production season when crop water needs are greatest. Weather-based approaches to scheduling irrigations are used for many cultivated crops. Windspeed, air temperature, relative humidity, and solar radiation affect plant water-use, or more specifically the water lost by evaporation from the soil and by transpiration from the leaves of the crop. Using evapotranspiration (ET) data (evaporation + transpiration) from the California Irrigation Management Information System (CIMIS) the consumptive water use of a crop in units of inches or mm per day, can be estimated.
CIMIS ET data is available from the Department of Water Resources website (http://wwwcimis.water.ca.gov/cimis/welcome.jsp) for more than 120 locations in California, and is generated by weather stations located on irrigated grass, which serves as a reference crop. The MyCIMIS feature of the website allows the user to customize the reporting of CIMIS crop ET data, such as specifying type of weather data, stations, time period, and file format to display. MyCIMIS also allows the user to select for the data to be emailed to their account. Spatial CIMIS is another feature of the website that produces estimates of reference ET at a 2 km (1.2 mi) resolution using GOES satellite information and by triangulating humidity, temperature and wind speed data from the closest CIMIS stations to the point of interest. A Google map feature allows the user to locate a field of interest. Similar to MyCIMIS, a user can select to have updated Spatial CIMIS estimates of reference ET emailed.
ET can be estimated for a specific crop by multiplying reference ET data and the appropriate crop coefficient (Kc):
ETcrop = ETref × Kc
The value of Kc can range from almost 0 to greater than 1 and is closely related to the percentage of ground shaded by the canopy. Irrigation method and physiological stages, such as flowering and senescence are also factored into the crop coefficient. Crop ET values should be adjusted down by 20% to 30% for crops grown under macro tunnels or greenhouses because of shading.
Because accurate crop coefficients are not available for many crops, estimates of canopy cover serve as a close substitute for the Kc values. We have taken overhead photos of the UC strawberry variety Albion using an infra-red camera during the last 2 years. Photos were taken on a monthly schedule for fields with 48-, 52-, and 64- inch wide beds. After analyzing canopy images from 9 fields, we have estimated the Kc values on a weekly schedule during a 12 month period (Table 1). Because these data represent the average of several fields, values may need to be adjusted for site-specific conditions. Also, these Kc values for Albion represent Salinas and Pajaro Valley growing conditions and methods.
By irrigating enough to replace water lost by evapotranspiration it is possible to optimize irrigations for production and minimize percolation below the root zone. Also, it is possible to avoid under-irrigating during periods of high water consumption, which can result in stress and reduced growth. ETc estimates can be used to determine day by day soil water depletions from field capacity and thus can be used to also estimate when to irrigate. For detailed descriptions and examples of this technique, visit http://wwwcimis.water.ca.gov/cimis/infoIrrSchedule.jsp
Table 1. Estimated crop coefficient (Kc) for UC strawberry variety Albion.
48-inch bed width | 52-inch bed width | 64-inch bed width | |||||||
Plant Date | DAP | % canopy cover | Kc | % canopy cover | Kc | % canopy cover | Kc | ||
11/1/2011 | 0 | 1 | 0.02 | 1 | 0.01 | 1 | 0.02 | ||
11/8/2011 | 7 | 1 | 0.02 | 1 | 0.02 | 1 | 0.03 | ||
11/15/2011 | 14 | 1 | 0.02 | 1 | 0.02 | 2 | 0.03 | ||
11/22/2011 | 21 | 1 | 0.03 | 1 | 0.02 | 2 | 0.04 | ||
11/29/2011 | 28 | 2 | 0.03 | 1 | 0.02 | 3 | 0.04 | ||
12/6/2011 | 35 | 2 | 0.04 | 1 | 0.03 | 3 | 0.05 | ||
12/13/2011 | 42 | 2 | 0.04 | 2 | 0.03 | 4 | 0.06 | ||
12/20/2011 | 49 | 3 | 0.05 | 2 | 0.04 | 4 | 0.07 | ||
12/27/2011 | 56 | 3 | 0.06 | 2 | 0.04 | 5 | 0.08 | ||
1/3/2012 | 63 | 4 | 0.06 | 3 | 0.05 | 6 | 0.09 | ||
1/10/2012 | 70 | 5 | 0.08 | 4 | 0.06 | 7 | 0.11 | ||
1/17/2012 | 77 | 5 | 0.09 | 4 | 0.07 | 8 | 0.13 | ||
1/24/2012 | 84 | 6 | 0.10 | 5 | 0.08 | 10 | 0.15 | ||
1/31/2012 | 91 | 8 | 0.12 | 6 | 0.10 | 11 | 0.17 | ||
2/7/2012 | 98 | 9 | 0.14 | 7 | 0.11 | 13 | 0.20 | ||
2/14/2012 | 105 | 10 | 0.16 | 9 | 0.13 | 15 | 0.23 | ||
2/21/2012 | 112 | 12 | 0.18 | 10 | 0.15 | 18 | 0.26 | ||
2/28/2012 | 119 | 14 | 0.21 | 12 | 0.18 | 20 | 0.29 | ||
3/6/2012 | 126 | 16 | 0.23 | 14 | 0.21 | 23 | 0.33 | ||
3/13/2012 | 133 | 18 | 0.27 | 16 | 0.24 | 26 | 0.37 | ||
3/20/2012 | 140 | 21 | 0.30 | 19 | 0.28 | 29 | 0.41 | ||
3/27/2012 | 147 | 23 | 0.33 | 22 | 0.32 | 33 | 0.46 | ||
4/3/2012 | 154 | 26 | 0.37 | 25 | 0.36 | 36 | 0.50 | ||
4/10/2012 | 161 | 29 | 0.41 | 28 | 0.40 | 40 | 0.54 | ||
4/17/2012 | 168 | 32 | 0.44 | 32 | 0.44 | 43 | 0.58 | ||
4/24/2012 | 175 | 35 | 0.48 | 35 | 0.49 | 47 | 0.62 | ||
5/1/2012 | 182 | 38 | 0.52 | 39 | 0.53 | 50 | 0.66 | ||
5/8/2012 | 189 | 40 | 0.55 | 43 | 0.57 | 54 | 0.70 | ||
5/15/2012 | 196 | 43 | 0.58 | 46 | 0.61 | 57 | 0.73 | ||
5/22/2012 | 203 | 46 | 0.61 | 49 | 0.65 | 60 | 0.76 | ||
5/29/2012 | 210 | 48 | 0.64 | 53 | 0.69 | 62 | 0.79 | ||
6/5/2012 | 217 | 50 | 0.66 | 55 | 0.72 | 65 | 0.81 | ||
6/12/2012 | 224 | 52 | 0.69 | 58 | 0.75 | 67 | 0.83 | ||
6/19/2012 | 231 | 54 | 0.71 | 61 | 0.77 | 69 | 0.85 | ||
6/26/2012 | 238 | 56 | 0.72 | 63 | 0.79 | 70 | 0.87 | ||
7/3/2012 | 245 | 57 | 0.74 | 65 | 0.81 | 72 | 0.88 | ||
7/10/2012 | 252 | 59 | 0.75 | 66 | 0.83 | 73 | 0.89 | ||
7/17/2012 | 259 | 60 | 0.76 | 68 | 0.84 | 74 | 0.90 | ||
7/24/2012 | 266 | 61 | 0.77 | 69 | 0.85 | 75 | 0.91 | ||
7/31/2012 | 273 | 61 | 0.78 | 70 | 0.86 | 76 | 0.92 | ||
8/7/2012 | 280 | 62 | 0.79 | 71 | 0.87 | 76 | 0.92 | ||
8/14/2012 | 287 | 63 | 0.79 | 71 | 0.88 | 77 | 0.93 | ||
8/21/2012 | 294 | 63 | 0.80 | 72 | 0.88 | 77 | 0.93 | ||
8/28/2012 | 301 | 64 | 0.80 | 72 | 0.89 | 78 | 0.94 | ||
9/4/2012 | 308 | 64 | 0.81 | 73 | 0.89 | 78 | 0.94 | ||
9/11/2012 | 315 | 64 | 0.81 | 73 | 0.90 | 78 | 0.94 | ||
9/18/2012 | 322 | 65 | 0.81 | 74 | 0.90 | 79 | 0.95 | ||
9/25/2012 | 329 | 65 | 0.82 | 74 | 0.90 | 79 | 0.95 | ||
10/2/2012 | 336 | 65 | 0.82 | 74 | 0.90 | 79 | 0.95 | ||
10/9/2012 | 343 | 65 | 0.82 | 74 | 0.90 | 79 | 0.95 | ||
10/16/2012 | 350 | 65 | 0.82 | 74 | 0.91 | 79 | 0.95 | ||
10/23/2012 | 357 | 65 | 0.82 | 74 | 0.91 | 79 | 0.95 | ||
10/30/2012 | 364 | 66 | 0.82 | 75 | 0.91 | 80 | 0.95 |