"Wisdom begins in wonder" – Socrates
Plant Wilting Point
08/21/25
“What’s the minimum amount of water in soil needed to keep plants alive?”
Plants require a specific amount of water in their root zone to survive. Otherwise, they’ll wither up and die. This quantity, defined by the Plant Withering Point, is affected by the soil type, plant species, and characteristics of the roots.
How to Calculate Power for Hydraulic Pumps
08/20/25
“How do we calculate power for hydraulic pumps?”
Hydraulic pumps are a pillar of modern water infrastructure. Through their mechanisms, they can create a pressure differential to match the needs of people. But pumps need power to operate, and we may need to calculate the power to accomplish what our goals. To do this, we can go to the simple physics equation (1) work = force * distance (W = F * h). Going further, we may notice that if we’re lifting a fluid, the force will be equal to (2) the fluid’s mass * gravity (m_fluid * g), and (3) mass of fluid = density of fluid * volume of fluid (m_fluid = rho_fluid * V_fluid). This is related to power through the equation (4) P = dW/dt, where Power is P. We can plug in equation (1) to (4) to make (5) P = d(F * h)/dt. → dF/dt*ht. If we substitute in equation (3), we get (6) P = (d(rho_fluid * V_fluid*g)/dt*h), and by (7) fluid flow = change in fluid over time (Q = dV_fluid/dt), we can substitute for (8) P = rho_fluid * g * h * dV_fluid/dt → P = rho_fluid * g * h * Q. And by remembering that (9) specific weight = density of fluid * gravity (Gamma_fluid = rho_fluid * g), we can finalize with (10) P = Gamma_fluid * Q * h. This is How to Calculate Power for Hydraulic Pumps. The pump’s efficiency will also affect this value.
Manning’s Roughness Coefficient
08/19/25
“How can we measure the resistance to fluid flow in channels and floodplains?”
Fluids flow through open channels in conduits and floodplains. The structures supporting fluid flow provide resistance to movement. The structure’s base surface roughness, stage and discharge, obstructions, geometric irregularities and alignment, vegetation, and debris contribute to fluid resistance. These are quantitatively summarized by Manning’s Roughness Coefficient, a variable vital for channel flow calculations. Manning’s roughness coefficients for various materials are found in engineering reference manuals.
Water Treatment Residuals
08/18/25
“What are the residuals left behind by drinking water treatment?”
Treating water for toxins is a vital part of modern infrastructure. However, these processes will leave behind Water Treatment Residuals such as coagulants or sediments. Water infrastructure engineers must handle these residuals to create a healthy, sustainable system.
Ponding
08/17/25
“What happens when water has no place to drain?”
Water will collect over land when there are insufficient infiltration capabilities. If this water has no place to drain, it will coalesce into a sizable puddle. This Ponding process can produce small bodies of water that can carry pollutants, become mosquito nesting grounds, and even damage building structures if it collects on a small roof.
Potential Maximum Retention
08/16/25
“How can we quantify the maximum amount of water a watershed can hold before runoff?”
Watershed geologies can hold a certain amount of moisture before runoff occurs. We can measure this through the Potential Maximum Retention, a hydrological quantity that represents the maximum amount of water a watershed can absorb before starting runoff.
Initial Abstraction (Hydrology)
08/15/25
“How can we quantify the initial rainfall losses before runoff begins?”
Rainfall will lead to water hitting the ground. Before anything happens, some of the rainfall will get intercepted by vegetation or infiltrate into the ground and get lost from the system. Hydrologists represent this value as the Initial Abstraction. Initial abstraction is an important quantity in hydroshed and stormwater studies.
Net Positive Suction Head (NPSH)
08/14/25
“What is the minimum pressure needed to avoid cavitation in pumps?”
If pumps don’t have enough pressure, then water vapor can form in the pumps and cause cavitation in the pump blades. Pumps can prevent this from occurring by maintaining pressure above the vapor pressure. The difference between these quantities is known as the Net Positive Suction Head (NPSH). The NPSH required (NPSH-R) is the pressure at the impeller entrance needed to avoid cavitation, equal to the difference between the stagnation pressure and the vapor pressure at the inlet. The Net Positive Suction Head Available (NPSH A) is the pressure available at the pump inlet above the vapor pressure and losses due to system friction. For functional system operation, NPSH A must be greater than NPSH R.
Static Pressure
08/13/25
“What’s the pressure of a fluid’s presence?”
Fluid pressure comes in all kinds of forms. Fluids will exert a pressure from their presence alone called Static Pressure. Air in a balloon is an example of static pressure.
Isaac's Science Blog 