Question

Sketch and label a graph illustrating changes in water levels in part of the High Plains aquifer from 1900 to 2000 . Assume that wells were not drilled into this part of the aquifer until 1940 and that the area is currently experiencing groundwater overdraft.

Short answer

The graph should feature a stable line from 1900 to 1940, a downward slope from 1940 to 2000, with increasing steepness near 2000 to depict overdraft.

Step-by-step solution

Understand the Timeline and Events

The question is asking us to sketch a graph of water levels in an aquifer from 1900 to 2000. Two critical points to note are that wells were not drilled until 1940, and that there is currently a groundwater overdraft. These will guide how we depict changes over time on the graph.

Sketch the Initial Water Level (1900-1940)

Since wells were not drilled before 1940, the water level in the aquifer would remain relatively stable during this period. On the graph, draw a horizontal line representing constant water level from 1900 to 1940.

Indicate Impact of Well Drilling (1940-2000)

In 1940, wells begin to be drilled, which changes the water level dynamics. After this point, the graph should show a decline in water levels due to increased extraction. Draw a downward sloping line from 1940 to 2000 to illustrate this decrease in water levels.

Represent Groundwater Overdraft

To indicate the current groundwater overdraft, ensure that the slope of the line becomes steeper as it approaches 2000. This reflects a rapid reduction in water levels, characteristic of overdraft situations where extraction rates exceed recharge rates.

Label Important Features on the Graph

Label key points on the graph: '1900-1940: Stable Water Level', '1940: Well Drilling Begins', '2000: Groundwater Overdraft'. This helps highlight the causes and effects of changes over time. Also, mark the years 1940 and 2000 on the x-axis and include units on the y-axis (for example, meters of water level).

Key concepts

Groundwater Overdraft

Groundwater overdraft occurs when water is extracted from an aquifer at a rate faster than its natural recharge ability. This creates a deficit between the amount of water being removed and the amount of water returning to the aquifer.
Over time, this leads to several issues:

• Decreased water availability for agricultural, industrial, and domestic use.
• Potential loss of water quality, as lower water levels may lead to contamination.
• Increased costs for drilling, as water is found at deeper depths.

Understanding groundwater overdraft is essential to manage water resources sustainably. If current trends continue, it could seriously impact both the environment and human populations. Managing this requires balancing water extraction with measures that support recharge, such as reduced usage or augmented natural processes through techniques like aquifer storage and recovery.

Aquifer Water Level Decline

Aquifer water level decline is a direct result of increased water extraction without sufficient recharge. As illustrated in our exercise, aquifer levels remained stable until 1940. Wells drilled thereafter began to draw water at a faster rate.
This decline is characterized by:

• Lower water tables, which make accessing groundwater more difficult and costly.
• Potential for subsidence, where the ground sinks, causing structural issues for buildings and infrastructure.
• Impact on ecosystems that rely on groundwater, such as wetlands and rivers.

Tracking water level decline over time helps in forecasting potential impacts and devising management strategies. A graph depicting this decline can visually represent the need for intervention to prevent further exhaustion of these crucial water resources.

Well Drilling Impact

Well drilling significantly changes the dynamics of groundwater systems. Before wells are introduced, aquifers typically have balanced recharge and discharge rates. Once wells start extracting water for various uses, this balance is disrupted.
The primary effects of well drilling include:

• Lowered water tables, needing more energy to pump water to the surface, increasing operational costs.
• Encouragement of further drilling, as neighbors notice reduced availability, leading to a race to deplete shared resources.
• Altered geological conditions near the well, which can influence local and regional water flows.

Strategically managed well drilling is crucial to prevent excessive impact on aquifer levels. Regulations or incentives may be necessary to ensure the ongoing viability of water sources for future generations.