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<br />"CA) <br />o <br />CO <br />o <br /> <br />j~<< About 6,000 acres of cropland sre not cultivated in anyone year. <br />Irrigation water is obtained mos':\y from the.Colorado River and is <br />del ivered to the fields through Federal and private canal systems <br />involving more than 200 miles of canals and over 500 miles of, <br />laterals. <br /> <br />3. Sal inity In The Grand Val ley <br /> <br />The valley 'contributes about 600,000 to 700,,000 tons of salt annually <br />to the Colorado River. It is assumed that most of these salts <br />(gypsum, calcite and sodium sulphate) are leached from the soil and <br />underlying Mancos shale and carried to the river by deep percolation <br />through over irrigation and by seepage from water del ivery and <br />tailwater collection ditches. Seepage losses from unlined farm <br />delivery ditches, taillolater collection ditches and deep p,ercolation. <br />from field irrigation are considered to be major sources of water that <br />carries salt to the river. Salt loading is the major cause of <br />sal inity increase in the Colorado River and has caused water qual i,ty <br />problems for downstream wa~er users. <br /> <br />4. Climatic Conditions <br /> <br />,. <br />::-.::.- ), <br />,. <br /> <br />Climatic conditions vary in different parts of the Grand Valley and <br />there is difference in temperature and precipitation between the east <br />and west end of the valley. In general, the area has hot summers, <br />mi Id winters, and a high percentage of sunny days. The hottest <br />temperatures occur in July and August and could go over 100 degrees <br />for several days. The coldest temperatures occur jn 'January and <br />February and readings below zero are not unusual. The cl imatic <br />summary for the Grand Junction area is presented in Appendix A. <br />Average monthly temperatures and precipitation since the M&E program <br />started are provided in this Appendix table. The average growing <br />season varies from 154 days to 190 days in different parts of the <br />Grand Valley. <br /> <br />The Grand Va I I ey has an ar ide I i mate and rece i ves between 8 to 10 <br />inches of moisture annually depending on the area. <br /> <br />In the I ast three to four years, extreme record 10101 temperatures in <br />February have been the norm. As a resu I t, the peach crop in the <br />va' I ey has been destroyed in the I ast two years because of the co I d <br />freeze. Other fruit trees and grapes have also succumbed to the cold. <br />In 1991, the temperatures were colder than normal (Apri I/May) in the <br />spring and delayed crop planting (e.g. corn) and growth by about two <br />weeks. Harvesting of corn was delayed by a few weeks because of cold <br />and wet fall (refer to c I i mat i c summary in Append i x A). <br /> <br />3 <br />