The article presents simple equations to calculate the difference in water level on both sides of a waterproof barrier during excavation dewatering. The researchers considered two scenarios: water level difference below the barrier and water level difference due to water flowing into the gap. By combining these scenarios, they found the total water level difference. The equations use factors like barrier depth, aquifer properties, and normal water flow. The researchers tested their method in a real-world case and found it to be accurate.