Pistachio Orchard Evapotranspiration Analysis

FAO-56 Penman-Monteith implementation for evapotranspiration analysis of a pistachio orchard in Torbat-e Heydarieh, Razavi Khorasan, Iran.

📍 Location

Parameter	Value
Site	Pistachio Orchard
City	Torbat-e Jam (تربت جام)
Province	Razavi Khorasan, Iran
Coordinates	35.2875° N, 59.2215° E
Elevation	~1,450 m above sea level

📊 Sample Output

Evapotranspiration Analysis

Summary Report

🔬 Methodology

This project implements the standardized FAO-56 Penman-Monteith method for calculating reference evapotranspiration ($ET_0$) and crop evapotranspiration ($ET_c$).

Key Equations

Penman-Monteith $ET_0$ (sub-hourly):

$$ET_0 = \frac{0.408 \cdot \Delta \cdot (R_n - G) + \gamma \cdot \frac{37 \cdot t_i}{T + 273} \cdot u_2 \cdot (e_s - e_a)}{\Delta + \gamma \cdot (1 + 0.24 \cdot u_2)}$$

Crop Evapotranspiration:

$$ET_c = K_c \cdot ET_0$$

Climate-Adjusted Crop Coefficient (FAO-56 Eq. 62):

$$K_{c\text{ mid}} = K_{c\text{ mid}(Tab)} + \left[0.04 \cdot (u_2 - 2) - 0.004 \cdot (RH_{min} - 45)\right] \cdot \left(\frac{h}{3}\right)^{0.3}$$

Implementation Details

Component	Method
$ET_0$	FAO-56 Penman-Monteith (adapted for sub-hourly intervals)
Crop Coefficient	Single Kc with climate adjustment
Solar Geometry	Full calculation (declination, equation of time, hour angle)
Net Radiation	Shortwave + Longwave balance
Soil Heat Flux	Simplified FAO-56 method (G = 0.1·Rn day, 0.5·Rn night)
Water Stress	Soil water balance with Ks coefficient
Date Handling	Automatic Persian (Jalali) to Gregorian conversion

🌳 Pistachio Parameters

Source: FAO-56 Table 12

Growth Stage	Kc	Description
Initial ($K_{c\text{ ini}}$)	0.40	Early season, sparse canopy
Mid-season ($K_{c\text{ mid}}$)	1.10	Full canopy, peak water demand
Late-season ($K_{c\text{ end}}$)	0.70	Pre-harvest, declining water use

Physical Parameter	Value
Tree height	3.5 m
Albedo (α)	0.20
Maximum root depth	1.5 m
Depletion fraction (p)	0.40

📈 Features

• Sub-hourly calculations: 10-minute interval ET computation
• Energy balance tracking: Rs → Rn → G → Available Energy
• Climate-adjusted Kc: Dynamic crop coefficient based on wind and humidity
• Soil water balance: Depletion tracking and stress detection
• Automatic date parsing: Extracts Persian (Jalali) dates from data
• Publication-ready plots: High-resolution visualizations
• Summary reports: Professional formatted output images

📦 Requirements

• Python >= 3.8
• numpy >= 1.21.0
• pandas >= 1.3.0
• matplotlib >= 3.5.0