Agenda - Council Work Session - 10/20/2020 - Special

Home

5.1.5.1 Well Drawdown Well drawdown is the decrease of water from the baseline static water level. It can also be described as a decrease in water elevation, potentiometric surface, or water head. As a well is pumped, drawdown is induced by the removal of a volume of water from the aquifer. As the well continues to operate it can also create an area around the well where water is drawdown. This area of drawdown is known as a cone of depression or the area of Influence from a pumping well. When a well discontinues pumping, water from surrounding aquifers wilt flow into the area and bring water levels back to static levels_ Pumping temporary creates an area of low potentiometric water pressure, and when the well is shut off water will flow into the area to balance out that change in potentiometric surface. This is known as recharge, or recovery. The recovery period like the drawdown is determined by the hydrogeological properties of the aquifer. Drawdown observed in the City of Rarnsey wells are typical for Twin Cities bedrock aquifers. The following chart depicts a drawdown and recover of Well 5 during a 2 day period starting May 3rcl to May 5th in 2019. Figure 3 — Terms Relating to Well Performance Flmnprg I TriEnum Sestlic WRGer LgWel - Di or -down 1:1.-nrsig kvel SIAN Icvc1 -60A A--krwir, ft m rt Figure 4 — Well 5 Drawdown and Recharge Subrottsible Pump Well 5 Drawdown and Recharge May 3 - May 5th 860 340 el 820 BOO • • 780 760 • 4- 1 • 7.10 720 700 0 10 0 0 0 0 0 0 CI 0 0 0 CD 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ct 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o a c.4 v.) A -A GI Cid in in ED CV .4.11 if/ 11— In ur. Q In act Q Q CO 11-1 Q Q CV Ili La E. 41 ,9 ,_z 6 tcli er' e6 L)8 ml g i4 2: e •• e• I e e e• e • 01, 0 V') c,,1 141 cNI tirr 'it.— .10 xi- t. to 00,1 L:e) 6o N. Go imp c, c n .6 co 600 66 fl to ci rg N 0.4N N linle FEASIBILITY STUDY -DRAFT Page 17 RAMSY 154354