Climate Modification of Dry Desert Air by a Large Irrigation Project

Climatic changes caused by the evapotranspiration of large amounts of irrigation water may be important in irrigation scheduling, weather forecasting and the management of irrigated farmland. Results from previous studies are often in disagreement as to the magnitude of climatic modification by irrigation. Some studies show only minimal changes (Fritschen and Nixon, 1967, Fowler and Helvey, 1974) and others show sizeable modifications (Davenport and Hudson, 1967). Beebe (1974) reports that severe storms as indicated by tornado's are more prevalent over irrigated land in Texas. A recent statistical report (Schickendanz, 1976) shows rainfall increases, temperature anomalities, and hail increases, all caused by irrigation. Schickendanz work covered a very large area in the Great Plains of the United States. Previously reported studies differ greatly in size of area involved and objectives. The studies reported here had the objective of showing the possible climate modification caused by a large irrigation project in Idaho surrounded by a nonirrigated sagebrush grass desert

Changes in Climate and Potential Evapotranspiration Across a Large Irrigated Area in Idaho

Ground level climatic measurements were taken along a 50 km transect going from dry sagebrush land into the center of a large irrigated area in southern Idaho. Measurements in May, when the desert area was dry, indicated that climatic changes across the transect were minimal. In August, when the desert was obviously very dry, air temperatures decreased, vapor pressure increased, and windspeed was reduced about 40 percent within the irrigated area. The results demonstrate that any weather service agency or group must consider the distance from dry surroundings when selecting sites that are to be representative of climatic conditions over irrigated fields

Water Requirements (Chapter 6)

The main objective of irrigation is to provide plants with sufficient water to prevent stress that may cause reduced yield or poor quality of harvest (Haise and Hagan, 1967; Taylor, 1965). The required timing and amount of applied water is governed by the prevailing climatic conditions, crop and stage of growth, soil moisture holding capacity, and the extent of root development as determined by type of crop, stage of growth, and soil

Irrigation Management -- Water Requirements and Water Balance

This paper seeks to discuss irrigation water requirement estimates in the light of current practice, important developments during the 1970's, significant research and future research and applications of that research. Each of these are elaborated in more detail in the text of this paper. A major addition to the science and art of estimating irrigation water requirements has been to replace the often ambiguous "potential evapotranspiration" with "reference crop evapotranspiration". In the past decade a series of experiments relating irrigation water applications to crop yield now permit a much better economic analysis of the use of water for irrigation. The estimation of monthly irrigation water requirements was facilitated, particularly for varying climatic conditions with the United Nations publication "Crop Water Requirements" by Doorenbos and Pruitt (1977). Estimation of daily water requirements for purposes of irrigation scheduling has been refined by the development of an albedo model and a wind function for the Penman method, that is variable throughout the season, Wright (1981). Several western states are experiencing lawsuits or other legal deliberations involving seasonal irrigation water requirements because of conflicts between groups of water users or water right transfers from agriculture to industry or municipal use. Irrigation scheduling continues to be refined from the standpoints of predicting ET, verifying yield conditions and other factors like production and peak pumping power reduction. Future research probably will include emphasis on breeding crops that require less water, refinements on the relationships between yields and water consumption, refinements in methods of estimating irrigation water requirements, and the development of irrigation schemes that minimize water and energy requirements. For other methods and more detail the reader is referred to sources such as Doorenbos and Pruitt (1977), Jensen (1974), Barman. et al. (1981)

Changes in Climate and Potential Evapotranspiration Across a Large Irrigated Area in Idaho

Ground level climatic measurements were taken along a 50 km transect going from dry sagebrush land into the center of a large irrigated area in southern Idaho. Measurements in May, when the desert area was dry, indicated that climatic changes across the transect were minimal. In August, when the desert was obviously very dry, air temperatures decreased, vapor pressure increased, and windspeed was reduced about 40 percent within the irrigated area. The results demonstrate that any weather service agency or group must consider the distance from dry surroundings when selecting sites that are to be representative of climatic conditions over irrigated fields

Water Requirements (Chapter 6)

The main objective of irrigation is to provide plants with sufficient water to prevent stress that may cause reduced yield or poor quality of harvest (Haise and Hagan, 1967; Taylor, 1965). The required timing and amount of applied water is governed by the prevailing climatic conditions, crop and stage of growth, soil moisture holding capacity, and the extent of root development as determined by type of crop, stage of growth, and soil

Irrigation Management -- Water Requirements and Water Balance

This paper seeks to discuss irrigation water requirement estimates in the light of current practice, important developments during the 1970's, significant research and future research and applications of that research. Each of these are elaborated in more detail in the text of this paper. A major addition to the science and art of estimating irrigation water requirements has been to replace the often ambiguous "potential evapotranspiration" with "reference crop evapotranspiration". In the past decade a series of experiments relating irrigation water applications to crop yield now permit a much better economic analysis of the use of water for irrigation. The estimation of monthly irrigation water requirements was facilitated, particularly for varying climatic conditions with the United Nations publication "Crop Water Requirements" by Doorenbos and Pruitt (1977). Estimation of daily water requirements for purposes of irrigation scheduling has been refined by the development of an albedo model and a wind function for the Penman method, that is variable throughout the season, Wright (1981). Several western states are experiencing lawsuits or other legal deliberations involving seasonal irrigation water requirements because of conflicts between groups of water users or water right transfers from agriculture to industry or municipal use. Irrigation scheduling continues to be refined from the standpoints of predicting ET, verifying yield conditions and other factors like production and peak pumping power reduction. Future research probably will include emphasis on breeding crops that require less water, refinements on the relationships between yields and water consumption, refinements in methods of estimating irrigation water requirements, and the development of irrigation schemes that minimize water and energy requirements. For other methods and more detail the reader is referred to sources such as Doorenbos and Pruitt (1977), Jensen (1974), Barman. et al. (1981)