The discharge per unit drawdown at the well is known as specific capacity.

Explanation:
The specific capacity of a well is a measure of its productivity and efficiency. It is defined as the discharge of water per unit of drawdown at the well. In other words, it represents the amount of water a well can produce relative to the amount of drawdown, or lowering of the water level, in the well.

Significance of specific capacity:
The specific capacity of a well is an important parameter in groundwater studies and well design. It provides valuable information about the aquifer properties and the performance of the well. By analyzing the specific capacity, engineers and hydrogeologists can assess the sustainability and potential yield of a well.

Factors affecting specific capacity:
Several factors influence the specific capacity of a well, including:
- Aquifer properties: The permeability and storage characteristics of the aquifer influence the flow of water into the well and, therefore, its specific capacity.
- Well design: The diameter, depth, and screen length of the well, as well as the presence of gravel packs or other filtering materials, can affect the specific capacity.
- Pumping rate: The rate at which water is pumped from the well can impact the drawdown and, consequently, the specific capacity.
- Aquifer recharge: The rate at which the aquifer is recharged by natural processes, such as rainfall or inflow from adjacent aquifers, can also affect the specific capacity.

Measurement of specific capacity:
To determine the specific capacity of a well, a pumping test is typically conducted. During the test, the well is pumped at a constant rate, and the resulting drawdown in the water level is measured. The discharge of water from the well is also measured. By dividing the discharge by the drawdown, the specific capacity can be calculated.

Conclusion:
The specific capacity of a well is an important parameter in assessing its performance and productivity. It is a measure of the discharge of water per unit of drawdown at the well. By analyzing the specific capacity, engineers and hydrogeologists can make informed decisions regarding well design and aquifer management.