With the ever-increasing sophistication and capacity of sensors and data logging and storage, along with the ever-expanding network of over-line transmission, it is becoming increasingly easy and affordable to collect and store environmental data. As water bec0omes a more precious commodity and water use pressing issue, weather data and related applications are becoming in valuable tools to many segments of society.
Agriculturists and nursery owners use the data to guide more efficient irrigation schemes. Civil engineers use it to resolve land suitability classifications and urban runoff issues. Environmental engineers model watershed dynamics and non-point source pollution. The list could go on.
Eventually, policy-makers use information from all these fields to determine water rights and other water quality issues. Perhaps the best way to illustrate current methods and applications is to outline some of the projects being undertaken by Engineers at the University of Georgia.
In 1991, the University of Georgia (UGA) initiated the development of an automated weather station network similar to networks that had been developed in other states. One of the main goals of this weather station network is to collect weather and other environmental data in areas where agriculture is being conducted. This not only includes traditional agriculture such as row crops, but also fruits and vegetables, ornamentals, turf for golf courses and recreational activities, and other non-traditional agricultural operations. The Georgia Automated Environmental Monitoring Network
(AEMN) has grown from four stations in 1991 too more than 45 stations in 2000.
Each station monitors air temperature, relative humidity, wind speed, wind direction, solar radiation, precipitation and soil temperature at three different depths. Some stations also monitor photosynthetic active radiation (PAR), net radiation, barometric pressure, pan evaporation and soil moisture.
The sensors are connected to a Campbell Scientific CR10 or CR10X data logger. The CR10 data logger provides two pulse channels and 12 single-ended channels for voltage readers. It has temporary as well as permanent memory that can store the program that controls its operation as well as the data that are being collected.
The data loggers can be programmed through small keyboard or a program can be uploaded through a serial port connection from a personal computer. A battery is used to power the system, and during the daytime, a solar panel recharges the battery. The data logger is programmed to collect the data from each sensor every second and the data are summarized at 15-minute intervals. At midnight, the daily totals as well as daily maximum, minimum and average values are calculated.
Communications are handed through a modem and wither a dedicated telephone line or cell phone that are connected to each data logger. A dedicated computer at the UGA College of Agricultural and Environmental Sciences Campus in Griffin communicates with each weather station on a continual basis.
After downloading the most recent data from the data logger to the personal computer, the data are processed immediately and spooled to a data server, as well as a web server. Users can view current weather conditions for more than 25 sites and retrieve daily data for all locations via the worldwide web www.georgiaweather.net.
The website of the AEMN provides: 1) current weather conditions; 2) a summary of the previous day or Yesterday’s Conditions; 3) a summary of the last four days, including maximum and minimum temperature, rainfall, average soil temperature at three different depths, wing speed and direction, solar radiation and potential evapotranspiration; and 4) a 30-day Summary table. Long-term daily data, including temperature and precipitation, can be downloaded under Historical Data.
Another group of applications includes the spatial products. These are based on an interpolation of the individual station data, using various software programs. Maps are provided for all daily variables. The maps are updated daily as new data becomes available
The most dynamic applications are the model-based products. One example is a water balance calculator. After selecting the site, a user can define the periods for which to conduct the calculation, both the starting date and ending date. Other calculators that have been implemented include a degree calculator in which the user can define both the base and maximum temperature and a chilling hour calculator. For application by utility and heating and air conditioning companies, a heating and a cooling degree day calculator are available with a fixed base.
For research applications, simulation models have been linked to the AEMN website. These models combine current weather data as well as historical weather data and provide growth and yield forecasts. AEMN data is also used to calculate site-specific evapotranspiration, which will be used in conjunction with soil moisture data being collected with Time Domain Reflectometry (TDR) soil moisture probes at nurseries. Soil moisture in containers will be correlated with weather data in an attempt to improve irrigation scheduling.
Another program at UGA is using small data loggers (HOBOs) along with manual data collection to attempt to document the amount of water used for irrigation by agriculture in Georgia. Results of this monitoring are being reported on an Ag Water Pumping website (www.agwaterpumping.net). These data, in conjunction with the AEMN data network, will provide critical information for those attempting to create sound water policy among the tri-state litigants of Florida, Alabama, and Georgia.
The precise and accurate collection, storage and transmission of important weather and water use data have become indispensable in the effort to create truly sustainable water use policies. In addition, as the different calculators on the AEMN websites demonstrate, this automatically sensed and stored data can be an important tool for many different engineering applications.
The Georgia Engineer, August/September 2001.