Laserfiche WebLink
mean NH3-N was not detected and 0.025 mg/L, <br />respectively; and mean TKN was 0.276 and 0.309 <br />mg/L, respectively. <br />The nitrogen to phosphorus ratio (N/P) is often used <br />to characterize an aquatic environment as being <br />either "phosphorus limited" or "nitrogen limited." <br />Lambou et al. (1976 [23]) suggests the following <br />criteria for N/P ratios: <br />• N/P>14 indicates a largely phosphorus- <br />limited environment <br />• N/P<10 indicates a nitrogen limited nutrient <br />• 10<N/P<14 indicates a "transition" environ- <br />ment, or one that is "co-limited" <br />Where table 16 shows TIN/TP and TIN/PO4-P where <br />total inorganic nitrogen (TIN) is the summation of <br />N02-P, N03-N, and NH3-N. <br />The Palo Verde Irrigation Drain had a TIN/TP of 7.6 <br />that indicated a nitrogen-limited environment. For <br />all other stations, TIN/TP was greater than 14 and <br />indicated phosphorus-limited conditions. <br />Figure 15 displays the concentration of POM found <br />above, in, and below the Palo Verde Irrigation Drain <br />during phase 2. Four of the five sampling dates (Jan.- <br />Aug. 1988) had greater POM concentrations in the <br />drain than either above or below the drain; mean <br />value in the drain was more than twice the mean <br />for the two river stations. The exception to this <br />occurred during a local rainstorm in August 1988, <br />which is discussed under subparagraph: Storm <br />Events. The majority of total POM comprised the <25- <br />µm size-fraction at all three stations. The Palo Verde <br />Irrigation Drain had the greatest concentration (3.54 <br />g/m3) and the highest percentage (89.5%) of <25- <br />pm POM as compared with Cibola and DR3. Similar <br />trends were observed in the total inorganic matter <br />with the highest concentration being found in the <br />Palo Verde Irrigation Drain (37.8 g/m3 in-drain <br />versus 22.0 g/m3 above and 21.1 g/m3 below). <br />Despite these obvious differences between the Palo <br />Verde Irrigation Drain and the main river channel <br />stations, table 15 shows that the drain had only <br />subtle effects on conditions downstream. For <br />example, mean temperature in the drain was <br />23.8 °C, which is 3.8 °C greater than the mean <br />temperature at Cibola. At DR3, the mean tempera- <br />ture also was greater than that for Cibola, but only <br />by 0.7 °C. Similar changes can be noted for almost <br />every parameter in table 15. Nutrients that entered <br />the river from the Palo Verde Irrigation Drain were <br />PHASE 2, 1988 <br />CIBOLA lob- drain) <br />® PALO VERDE IRRIGATION <br />DRAIN (in-drain) <br />DR3 (below drain) <br />E <br />rn 4 <br />f <br />3 <br />0 <br />JAN MAR MAY JUN AUG MEAN <br />Figure 15.-Concentration of POM at Cibola, in Palo <br />Verde Irrigation Drain, and at DR3 during phase 2 <br />(Jan. through Aug. 1988). <br />Table 16.-Mean total inorganic nitrogen TIN, TP, P04-P, and ratios TIN/TP and <br />TIN/P04-P for the entire study period. <br />Station TIN <br />mg/L TP <br />mg/L P04-P <br />mg/L TIN <br />TP TIN <br />P04-P Remark <br />Davis Dam 0.368 0.007 0.001 52.6 368.0 PLf <br />Park Moabi .358 .011 nd" 32.5 - PL <br />Havasu Delta .382 .007 .002 54.6 191.0 PL <br />Parker Dam .311 .011 nd 28.3 - PL <br />Headgate Rock Dam .308 .014 .003 22.0 102.7 PL <br />Palo Verde Diversion Dam .293 .007 .001 41.9 293.0 PL <br />Cibola .324 .009 nd 36.0 - PL <br />Palo Verde Irrigation Drain .644 .096 .021 6.7 30.7 NO <br />DR3 .400 .013 .003 30.8 133.3 PL <br />Imperial Dam .316 .011 .006 28.7 52.7 PL <br />All American Canal .373 .011 .004 33.9 93.3 PL <br />Laguna .316 .013 .003 24.3 105.3 PL <br />Yuma .412 .010 .002 41.2 206.0 PL <br />. nd = Not detected at detection limit: where P04-P = 0.001 mg/L <br />t PL= Phosphorus limited. <br />t NL= Nitrogen limited. <br />21