Independence and Liberty, Missouri Well Fields CRA [46430kb]
The shape of the total CRA for the Independence, Missouri well field is roughly a half-circle bounded by the alluvial valley wall to the south and by the Missouri River to the north with part of the total CRA that extends across the Missouri River to the west for each pumping, river-stage scenario and indicates that flow beneath the river occurs. The greatest changes in the total CRA occur in the area across the river and to the west of the well field. However, the entire river bend within the confines of the alluvial valley walls to the south and the Missouri River to the north with the exception of a small area on the extreme eastern edge are a part of the total CRA for all pumping, river-stage scenarios. Induced recharge from the Missouri River is indicated by the 1- and 5-year CRAs located next to the Missouri River for all scenarios.
The location and shape of the total CRA across the river is different for each scenario and is effected not only by pumping and river stage, but also by the low ground-water gradient west of the well field across the river and the possible interference from the CRA of the Liberty, Missouri well field located north of the Independence, Missouri well field. The effect of this interference is shown in the comparison of the two total CRAs between scenarios. The total CRA for the HPLR scenario is located along the southwest edge of the total CRA for the Liberty, Missouri well field in a narrow band approximately 0.25 to 0.5 kilometer wide and almost 5 kilometers long. When pumping rates are decreased in the LPLR scenario, the total CRA across the Missouri River for the Independence, Missouri well field moved to the north in response to the decrease in size of the total CRA of the Liberty, Missouri well field and expanded to approximately.5 to 1 kilometer in width. The effect of changes in pumping rate on the location of the total CRA across the Missouri River is greater for the high-river stage scenarios because of the relatively low ground-water gradient. The total CRA across the Missouri River for the LPHR scenario extends to the west of the well field and is approximately 6.5 kilometers long and up to 1 kilometer wide. However, the total CRA across the Missouri River for the HPHR scenario is much smaller and is composed of only a few areas located next to the north alluvial valley walls. The decrease in the Independence, Missouri well field total CRA in the HPHR scenario was caused by the diversion of ground water toward the Liberty, Missouri well field illustrated by the increase in the total CRA for the Liberty, Missouri well field for this scenario.
Simulated pumping rates for the Independence, Missouri well field range from 38,816 m3/day for the QUASI scenario to 112,864 m3/day for the high pumping scenarios.The total CRA ranged from 6.39 km2 for the HPHR scenario to 9.406 km2 for the LPHR scenario.
The total CRA for the Independence, Missouri well field decreased with increased pumping for both high- and low-river-stage scenarios, increased with river-stage increase for the low-pumping scenarios and decreased with river-stage increase for the high-pumping scenarios. The 1-year CRA was smallest for the QUASI scenario when pumping rates were also small and increased but remained the same for the two low pumping scenarios.
The change in size of the Independence, Missouri well field total CRA with respect to changes in pumping and river stage is similar to the behavior of the Missouri Cities Water Company well field total CRA when the ground-water gradient was low. As previously discussed, the decrease in the total CRA for the HPHR scenario is explained by the combined effect of a low ground-water gradient across the Missouri River, west of the Independence, Missouri well field and the increased pumping of the Liberty, Missouri well field. This resulted in a decrease in the altitude of the potentiometric surface across the Missouri River from the Independence, Missouri well field so that the gradient beneath the Missouri River was removed and the water that previously discharged to the well field, instead discharged into the Missouri River.
The shape of the total CRA for the Liberty, Missouri well field is roughly oval, is longest in an east-west orientation, and is bounded on the north by the alluvial valley walls. The dimensions of the total CRA range from approximately 6.5 kilometers long by 3 kilometers wide to approximately 8 kilometers long by 4 kilometers wide. The total CRA is skewed to the west and, for the HPLR scenario, the well field is approximately 5 kilometers from the western edge and approximately 3 kilometers from the eastern edge of the total CRA. The total CRA for the Liberty, Missouri well field is large compared to other total CRAs in the study area. This is because little or no water is supplied to the well field through induced recharge from the Missouri River. Therefore, the total CRA extends well into the surrounding aquifer. No 1-year CRA exists for any of the pumping, river stage scenarios because the area where the wells are located has a relatively thick upper layer of clay and silty clay that inhibits rapid downward movement of water from the surface of the water table to the screened interval of the pumping wells. The 5-year CRA is centered around the well field for all pumping, river-stage scenarios. The 10-year CRA is located in two areas; one centered around the well field and the other approximately 1 kilometer to the south west of the well field. The presence of the 10-year CRA to the south west of the well field with a 100-year CRA between is explained by an area of higher hydraulic conductivity silt and sand in the same location in the upper parts of the aquifer. This allows surface recharge from rainfall to enter the aquifer and move to the screened interval of the wells more quickly than in other nearby areas. The 100- and 1000-year CRAs make up the majority of the total CRA in all scenarios.
Simulated pumping rates for the Liberty, Missouri well field range from 7,950 m3/day for the low pumping scenarios to 13.254 m3/day for the high pumping scenarios. The total CRA ranged from 14.874 km2 for the LPHR scenario to 23.469 km2 for the HPHR scenario. The total CRA for the Liberty, Missouri well field increased with increased pumping for both river stage scenarios, decreased with increased river stage in the low pumping scenarios, and increased slightly with increased river stage for the high pumping scenarios.
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Updated: September 5, 2003
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