4. Explain the concept of infiltration capacity (i.e. infiltration capacity curv
ID: 152635 • Letter: 4
Question
4. Explain the concept of infiltration capacity (i.e. infiltration capacity curve). A constant low steady drizzle type rain occurs in Seattle, Washington. The soils in the region are characterized by a relatively permeable sand. a. In terms of infiltration capacity and precipitation rate, which example best describes this situation. There are 3 primary cases (or examples) of this. Can you describe each case and explain which example best describes the situation in Seattle, Washington? [4] b. Can you describe each case and explain which example best describes the situation with Hurricane Katrina, in which there were record high rainfall rates measured? [2] C. How does infiltration capacity influence soil and groundwater remediation efforts? [1]Explanation / Answer
Answer 4) Infiltration capacity is the maximum rate at which water can be absorbed by a given soil per unit area, under given condition. It is usually measured by the depth(mm) of the water layer that can enter the soil in one hour. In general, the infiltration capacity of dry soil is higher.
Answer a) A permeable sandy soil will have higher rates of infiltration. Since sand is a porous material it can accommodate a lot of water in its pore space. Thus infiltration capacity of sand is high. A continuous soft steady drizzle will hence effect the sandy soil. A lot of water will be infiltrated according to its capacity, when the precipitation exceeds the infiltration capacity there is surface runoff.
Case 1- Infiltration rate is more than precipitation
In this case the permeable sand in Seattle will infiltrate maximum water. If rainfall 8s less, then the sand can restrict the rate of infiltration as there is no water for ponding. Thus the soil moisture won't be adequate, leading to relatively dry sandy soil.this is an example of steady soft drizzle in Seattle.
Case 2- Infiltration rate is equal to precipitation.
In this case the soil is neither underestimated nor over saturated with moisture
Case 3- Infiltration rate is lower than precipitation.
In this case, the excess water from precipitation won't be infiltrated, as the infiltration capacity of permeable sand in Seattle would be over.thus the excess water would be present in the form of surface runoff or ponding.the sandy soil would have adequate moisture. This is an example of heavy rains in Seattle.
Answer b) Hurricane Katrina brought very heavy rains in the state of Louisiana's. The measured rainfall was about 200-250mm. The highest rainfall recorded was 380mm.This c is similar to the case where the rate of precipitation is much higher than the infiltration capacity. Louisiana has mainly permeable sandy soil, with high infiltration capacity. The rains exceeded the infiltration rate. The area was flooded and heavy rains occurred continuously.
Answer C) Infiltration capacity can directly affect soil and groundwater. Sand is permeable and has the maximum infiltration capacity due to its high porosity, hence it will absorb more water. This will hence result in a higher amount of soil . moisture. The water will percolate further, and will act as a recharge to the aquifer. Thus sandy soil are better aquifer than clay, since it has both porosity and permeability. Hard rock terrain will have lower infiltration rates, due to lower porosity and permeability, thus they won't be potential groundwater aquifers.
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