Soil Infiltration and Runoff

Name: Frederick J. Baker III

Date: 6/6/18   

Instructor’s Name: Professor Kristen Hathcock

Assignment: SCI103 Phase 3 Lab Report

Title: Soil Infiltration and Runoff

Instructions: Enter the Virtual Lab and gather the information needed to complete the report from the field. Please type your answers. When your lab report is complete, submit it to the Submitted Assignments area of the Virtual Classroom.

Part I: Field Research

Section 1: Gather the following information from field research while in the Phase 3 lab environment. Notice that each site you visit has a distinctly different surface, which could affect runoff.

Section 2: One inch of rainfall deposits 144 cubic inches (0.623 gallons) of water per square foot of surface area. Use the following formula to calculate the amount of water after one inch of rainfall (in gallons) for each section:

(0.623) x (square feet of surface area) x (% from lab demo*) = gallons of water

*Remember 40% is written as “0.40” in an equation.

Part II: For the following questions, provide your response in a short-answer format (3–5 sentences each). Use this Phase’s activities and resources to assist you in answering.

1. How does the vegetation surface type affect the amount of runoff? Speculate why this happens.

In the vegetation surface type, the runoff is 10%, which is lower because plants, leaves, and other vegetation types hold the water from the rain, preventing it from hitting the ground. This also allows for more water to be absorbed by the soil. Therefore, vegetation retains precipitation and reduces the runoff rate. Plants and other vegetation hold rainwater for longer periods, allowing the soil to have sufficient time to absorb the water and prevent a lot of runoff. This process is also known as infiltration. This means that as the soil is covered by more vegetation, there is likely to be less runoff until the water capacity is achieved, and the surface starts allowing for more water to flow away from the plants.

Data from Part I also show that shallow and deep water infiltration was much higher in the vegetation surface than other surfaces. This is because the vegetation surface has a high amount of evaporation due to retaining high amounts of water than the other surfaces.

2. How does the smooth mountain rock surface type affect the amount of runoff? Speculate why this happens.

The smooth mountain rock surface does not allow water to infiltrate the soil because it has fewer cracks and is solid. It, therefore, allows water to run off into other areas. Contrary to the vegetation surface, the smooth mountain rock surface lets water runoff happen quickly downhill because fewer obstacles are not as porous as the soil. This situation causes more water to reach the soil, thus speeding up the infiltration rate as the absorption capacity is met quickly. The smooth mountain rock surface also topples the rate of runoff faster than the vegetation surface due to very minimal absorption. Such a situation can lead to flooding and increase the overflow in lakes and rivers because there is little water absorption by the soil.

In the smooth rock surface type, the runoff rate is 60% because, unlike the vegetation type, these surfaces have smaller openings in their surfaces, thus allowing for little water absorption and more runoff.

Data from Part I also show that the mountain has the lowest evaporation rate.

3. How does the bare soil surface type affect the amount of runoff? Speculate why this happens.

In the bare soil surface type, the rain may compact the bare soil, causing an increase in the runoff rate. This type of surface has little plant and vegetation to help slow the runoff. As such, precipitation sinks into the bare soil surface until the soil cannot absorb any more water. When the precipitation rate is higher than the soil can allow, there is runoff downhill or the other stationary areas. In cases where the soil is denser, such as clay soil types, the runoff rate will be higher because the water will only infiltrate small holes and cracks present on the ground.

In the bare soil surface type, the runoff amount is 35% since more water infiltrates the soil because it lacks vegetation or nutrients.

Data from Part I also show that the evaporation rate is at 30%

4. How does vegetation slow and prevent sediment loss?

The leaves, branches, grass, roots, and petals from plants help to capture precipitation. Depending on how much water this vegetation consumes, the above variables may continually start to slow runoff and stick to the sediment to maintain the root system and keep it stable.  The vegetation’s root system generally holds sediment in place, acting as a control system under extreme weather conditions that would displace the sediment on other occasions.

5. How does vegetation allow greater infiltration?

In vegetation type surfaces, the infiltration rate is higher because the leaves, branches, petals, and roots have the power to hold the water and prevent it from directly hitting the ground. This holding capacity allows the water held in the soil to get saturated, thus allowing for more absorption by the vegetation. Also, vegetation also allows the soil to be porous due to the roots, thus allowing for more room for water during infiltration.

6. How does pavement or smooth rock runoff affect waterways?

Runoff water from smooth surfaces allows more water to get to the waterways because there is the absence of obstacles and the surface is also non-porous. This allows for pollutants and garbage to move into the water system easily, thus contaminating the water that animals, plants, and humans depend on for their survival. The lack of obstacles such as vegetation can sometimes cause the runoff to get into waterways and cause flooding.

7. How do heavy sediment deposits affect waterways?

Heavy sediment deposits may result in clogging, especially if they are, they become thick as a result of compilations. Smaller deposits may sink directly to the waterway’s bottom and get compiled over time. Such situations may result in flooding because once the drainage gets blocked, bacteria and other pollutants thrive over time.

8. How does sediment loss affect land and soil quality?

The sediment contains vital organic nutrients that are necessary for healthy plant life. Without proper nutrients to help them sustain themselves, vegetation will quickly die out. For instance, carbon is important for generating bacteria that create and transfer nutrients that are essential for plant survival.

Reference

Martonas, J. (2017). How Does Sediment Affect the Ecosystem? Retrieved from https://sciencing.com/sediment-affect-ecosystem-6772.html