Tunis

Nabeul

Sousse

Bizerte

Rainfall amount (mm/year) and Ecartype

449.7/122.4

468.1/160.4

328.1/137.8

634.6/153.3

ET₀-PM (mm/year)

1424

1485

1527

1334

Frequency of water recovery following the stage of development

March: 40% April-June: 1% July-August: 0% Sept-Nov.: 33% Dec-Feb.: 91% Annual: 1%

March: 28% April-June: 0% July-August: 0% Sept-Nov.: 39% Dec-Feb.: 80% Annual: 14%

March: 17% April-June: 0% July-August: 0% Sept-Nov.: 24% Dec-Feb.: 36% Annual: 0%

March: 56% April-June: 0% July-August: 0% Sept-Nov.: 59% Dec-Feb.: 99% Annual: 19%

Lower relative variation of ET₀ in comparison with PM

Ivanov: +0.3% Turc: +12.4%

BC: −4.2% Ivanov: +28%

Ivanov: −1.8% Turc: +20.8%

Chr. Harg. = +1.6% Ivanov: +3%

Formula giving the lowest seasonal deficit

Ivanov Turc

Ivanov Harg Sam

Chr Harg =

Turc

Ivanov Turc-Harg Sam

P-ETc > 0 for 1 - 2 years (annual)

All methods except EAG

All methods except PO and EAG

All methods except EAG

All methods

P-ETc > 0 for 3 - 5 years (annual)

All methods except EAG–PO-BC

Turc-Ivanov Chr Harg Harg Sam

Turc Chr Harg Harg Sam

All methods except EAG

P-ETc > 0 for 6 - 10 years (annual)

Turc Chr Harg

Ivanov

-

All methods except EAG, PO et BC

Adopted formula

Turc

Ivanov

Turc

Ivanov

r value correlation with PM

0.992

0.950

0.981

0.961

Best correlation with PM

ST and SW r = 0.999

ST and SW r = 0.997

ST and SW r = 0.996

ST and SW et BC r = 0.999

Adopted formula following the stage of development

(low relative variability)

Stage 1: Chr Harg.

Stage 2: Harg Sam O.

Stage 3: PO Stage 4: ST and SW Stage 5: Turc

Stage 1: BC Stage 2: ST and SW Stage 3: Chr Harg Stage 4: BC Stage 5: BC

Stage 1: BC Stage 2: BC Stage 3: PO Stage 4: BC Stage 5: BC

Stage 1: ST and SW Stage 2: Harg Sam Stage 3: PO Stage 4: ST and SW Stage 5: Turc

Adopted formula

Turc HR > 50%

HR < 50%

R_s = (0,.25 + 0.5 n/N) × R_a

Ivanov ET_o = 0.0018 × (T + 25)²

× (100 × e/e^o 100)

Turc HR > 50%

HR < 50%

R_s = (0.25 + 0.5 n/N) × R_a

Ivanov ET_o = 0.0018 × (T_m + 25)²

× (100 − e/e^o 100)

Variables involved

T_m, RH_average, R_a, n, N

T, e, e^o

e^o (T) = 0.6108 exp (17.27 × T)/(T + 237.3)

e = e^o × RH_average/100

T_m, RH_average, R_a, n, N

T, e, e^o