SWMM5 CN Code for Infiltration Rate

 📌 Purpose of the Code:

This code 🖥 calculates the infiltration rate using the Curve Number method for a specific patch of land, known as a subcatchment. 🌍💧

📂 Inputs:

• infil: 📦 A pointer to the Curve Number infiltration object.
• tstep: ⏳ The runoff time step in seconds.
• irate: ☔ The rainfall rate in feet per second.
• depth: 🌊 The depth of runon + ponded water in feet.

📂 Output:

• Sends back 🚀 the infiltration rate in feet per second.

🔍 Detailed Breakdown:

1️⃣ Initial Setup:

• A few local variables like F1 and f1 are initialized. 📊
• fa gives us the max available infiltration rate, considering both the rainfall 🌧 and the effect of ponded water over time. ⌛

2️⃣ Rainfall Case (irate > ZERO):

• New rainfall? 🌦 Reset values! Resets the cumulative precipitation (P), infiltration (F), rate (f), and storage depth (Se).
• Update the total rainfall amount 📈.
• Compute potential new cumulative infiltration 📉.
• Determine the infiltration rate 💧.

3️⃣ No Rainfall Case (else):

• If water's still around 🌊 (but no new rain), the infiltration rate sticks to the last known value but within storage limits.
• If everything's dry 🌵, the time since the last rain (T) gets an update.

4️⃣ Infiltration Update:

• Got some infiltration? 💦 Limit the rate considering the max available rate.
• Make sure the total infiltration (F) gets updated 📝.
• If there's a regeneration constant given, the infiltration capacity (S) takes a dip 📉.

5️⃣ Infiltration Capacity Regeneration:

• No infiltration? Time for the capacity (S) to regenerate 🌱, based on a given constant and the max storage.

6️⃣ Return Value:

• Update the current infiltration rate (f1) for the object and send it back! 🎉

📝 Summary: This nifty function 🖥 computes the infiltration rate in a patch of land using the Curve Number method. It dances 💃 between rainfall and no-rainfall scenarios, adjusting the infiltration capacity as needed. And voilà! It sends back the updated rate. 🌧💧🌱

There we go! A sprinkle of emojis for added flair! ✨🎉🎈 Hope it helps! 😊🌟🎈