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w ~.. ~ QQ after the first irrigation. However, most sites were over- irrigated enough to cause considerable deep percolation and reduce application ,efficiency. This is discussed in more detail under irrigation adequacies at sites. Deep Percolation: Irrigation data collected from monitoring sites in 1993 shows that about one-third of the farmers over-irrigated.. heavfly. Over half (;f the' irrigators had 10.... deep percolation. and under-irrigated most of the time. The remaining i~rigators had . medium deep percolation and under-irrigated or over-irrigated at .times. . The seasonal deep percolation losses for the 22 sites are shown in Table 2 ....hich has been extracted from individual irrigation summaries provided in Appendix D. Also, detailed deep percolation values for each surface irrigated site by irrigation events are provided in Table 3. These are shown in two formats, as acre inches per acre and as a percentage for each individual irrigation event. . . '~~ ~ . The average annual deep percolation in the Grand Valley ....as originally estimated to be 11 acre inches per acre, which results in approximately four tons of salt pickup per acre foot (see Appendix F) reaching the Colorado River. Ho....ever, monitoring data for the last nine years indicate the average deep percolation to be slightly less than 16' acre inches per acre. (Table 4). '. . , Irr 1"993, the av~rage deep percolation foral'l 22 s1 tes' which' consisted of '20 surface sites and 2 sideroll sprinklers ....as 11.8 inches (Table 2); a decrease of 4.9 inches p~r acre compared to 1992. The 20 surface sites consisted of 8 sites with surge system and 12 without surge (conventional irrigation). Deep percolation for the 12 conventional sites was 18.5 inches and 4.3 inches for the 8 surge sites (Table 2). A reduction of 14.2 inches per acre in deep percolation was achieved with surge 'irrigation. The average for ,the two'sprinkler' sites was 1.2 inches (Table 2). The deep percolation valuessho....non Tables 2 and 4 are average values obtained from both surface and sprinkler irrigated sites. Irrigation data from the 22 monitoring sitessho.... that 11 of the fields had deep percolation of less than 5 inches, three fields had between 5 and 10 inches deep percolation and eight fields had over 10. inches of deep percolation. - The median deep percolation is about 9.9 inches. sites 26/51, 56, and 61 had 10.... deep percolation losses because of under-irrigation after the first irrigation of the season., However, actual field moisture determination witn.the hand feel method at sites 26/51 and 61 during the irrigation season showed '! 16 I I I ......:;.. ~:.~~?51 I I I I ~:~\;~. I I I I I I