Rainy day

We had our first real thunderstorm this morning and its been raining since.  Its so tough to get out bed when you can hear the rain and the thunder outside.  Of course when you've been up with your daughter for two hours in the middle of the night AND its raining and thundering its even tougher.

As a new home owner and someone who is now obsessed with his yard, its of note that this is the second major rain we've had this spring.  About 10 days ago we had a slow 3/4" rain that fell all night.  Now today we are already at more than 1" of rain since 7am (its now 12:00).  This rain fall has been a little more intense than the one 10 days ago, though we still haven't had more than 1/10 of an inch in any 15 minute period.  So this leads me to ponder.... what is the ideal rain rate for your grass?  How fast is too fast?  Is there a point that it goes from just not being ideal to being a problem?

For my Kentucky Blue, it needs one to one and one half inches of rain a week, at least in the heat, so we'll go with that as a good measure for now too.  Also, the ideal watering depth is six to eight inches into the soil which is what you get in a loam (read ideal) soil with one inch of rain.  In loam soil its supposed to take two hours for the soil to absorb an inch of rain.

That' the simple analysis of our rain today.  Then there's the technical analysis.

The general hydrologic budget, with all the components, with respect to infiltration F. Given all the other variables and infiltration is the only unknown, simple algebra solves the infiltration question.

F = B_I + P − E − T − ET − S − R − I_A − B_O

where

• F is infiltration, which can be measured as a volume or length;
• B_I is the boundary input, which is essentially the output watershed from adjacent, directly connected impervious areas;
• B_O is the boundary output, which is also related to surface runoff, R, depending on where one chooses to define the exit point or points for the boundary output;
• P is precipitation
• E is evaporation
• ET is evapotranspiration
• S is the storage through either retention or detention areas
• I_A is the initial abstraction, which is the short term surface storage such as puddles or even possibly detention ponds depending on size;
• R is surface runoff.

No thanks. I'm not ready for that kind of thinking. I'll just stick with my simple observation that this is a nearly perfect rain shower for my little "Patch-O-Grass"