Appendix

Sample calculation to determine required pond capacity
Sample calculation to estimate the volume of a pond
Equipment and recording forms for soil survey
Soil texture determination
Determination of hydraulic conductivity (k) for non-saturated soils
Slow sand filtration for water purification
Climatic data for 40 stations in Ethiopia

Sample calculation to determine required pond capacity*

Average number of households to use the pond = 50

Average size of household = 4.5 persons

Average water consumption for domestic purposes = 30 l/c/d**

Domestic requirement = 30 4.5 50 = 6750 l/d

Average livestock population per household = 8.3 TLU

Average livestock water consumption = 30 l/TLU

Livestock watering requirement = 30 8.3 50 =12 450 l/d

Losses from a pond of dimensions 60 60 3 m with sideslopes of 1:3 and 1:2 = 0.0088 51 54 (dimensions at mid-depth) = 24.23 m³/day

Required pond capacity = 6.75 + 12.45 + 24.23 = 43.43 m³/day or 1303 m³/month

Required pond capacity for dry season (November to May) = 9120 m³

This is the minimum size, a larger volume of water should be provided to allow for non-usable water. To allow the bottom 30 cm with a high silt content to remain in the pond a further 600 m³ would be needed giving a total capacity of 9720 m³.

* Data used from a PA in the Debre Berhan area.

** Increase in consumption with improved supply taken into account.

***Where evaporation and seepage losses are not known, the formula given in Section 2.1 can be used.

Sample calculation to estimate the volume of a pond

Prismoidal formula

The amount of soil to be excavated and the maximum capacity of the pond can be estimated

quite accurately provided the sideslopes are uniform.

V = D [A + (4 B) + C] /6

where:

Example

If the dimensions of a pond are 60 60 m, depth is 3 m and sideslopes are 1:2 at the sides and 1:3 at the upper and lower ends of the pond, then

V = 3 [(60 60) + (4 51 54) + (48 42)]/ 6

V = 3 16 632/6

V = 8316 m³

Middle-area formula

A faster but less accurate estimate of volume can be found by the middle-area formula

V = D A (middle)

where: D = average depth of pond (m)

A (middle) = area of excavation at mid

depth (0.5D) in m².

The amount of work required to excavate certain pond capacities can be easily calculated. Some values are given in Table B.1.

Table B.1. Soil volume to be excavated and work requirements for ponds of different dimensions.

^a 15 oxen-pairs scooping 8 m³/opd (oxen-pair day) =
120 m³/day; 15 oxen-pairs scooping 10 m³/opd =150 m³/day.
^b Pond aligned with 90 m length across the slope.
^c Pond aligned with 90 m length running downslope.

Equipment and recording forms for soil survey

Equipment

1. Soil auger with extension rods to allow sampling to a 4-m depth. Screw or cylinder (posthole) types of auger.
2. Water for hand-texturing of soil.
3. Notebook and soil survey forms (where available).
4. Tape measure (30 m minimum) and three ranging rods for marking out sample sites on a grid basis.
5. Plastic bags and labels for soil samples requiring further analysis.
   For soil permeability tests where soil clay content is suspected to be rather low for ponds:
6. A 50 ­ 100 litre water container.
7. Standard (see Figure E.1.) for measuring water level.
8. Metal tape measure.
9. Float for the end of the tape.
10. Wrist watch or stop watch.

Figure E.1. Inversed auger-hole method to determine hydraulic conductivity (K).

Soil survey recording format

Name of recorder:                                   Date:

Name/location of site:                              Peasant Association:

I. General information (underline relevant description and detail as necessary)

1. Land use: arable/fallow/ pasture (hay) /other:
2. Vegetation: (detail species present)
3. Catchment topography: flat/gentle/rolling/steep
4. Slope of site:◮^o/◮%
5. Surface hindrance: stones/boulders/rock outcrops/other:
   Extent of hindrance: none/little/moderate/ extensive
6. Evidence of erosion: runoff/surface crust/siltation/surface channels
   Extent of erosion: none/little/moderate/extensive
7. Water table: yes/no; if yes, depth of water table:.
8. Drainage: free/impeded
   Drains: none/few/many
9. Period of waterlogging:

II. Auger-hole samples

At each auger hole describe the following:

Soil structure: loose/granular/moderate


porous/compact

Nature of limiting material:

Effective depth:

For each distinctive layer describe the following:

Depth of soil layer:
Colour and mottling:
Soil textural class:
Root and stone content: none/few/many
Moisture condition: dry/moist/wet

III. Additional observations
(record any other relevant factors)

IV. Number of collected samples and their depth
(for those samples taken for further analysis).

Example of soil profile description

Soil texture determination

Manual texture test

Each sample should be hand-textured to determine the textural class . proportion of clay, silt and sand. A ball of soil about 2.5 cm in diameter should be taken and moistened with a few drops of water until it just begins to stick to the hand. The soil is then manipulated as described below; the extent to which the moist soil can be shaped is indicative of its texture. Besides hand-texturing, which is detailed in Figure D.1, a shaking test can also be used to distinguish inorganic silt from clay.

Figure D.1. Manual soil-texture text.

Textural class (see Figure D.1):

Other features of textural classes:

1. Loam or silt, when dry, gives off a fine powdery dust if scratched or blown upon, but a clay soil will not.
2. Loam, when wet, feels soapy and more or less plastic; when rubbed between the fingers until dry it leaves dust on the skin; clays do not.
3. Clay, when augered, displays shining faces if it has a slightly moist condition; a loam does not.

Shaking test

1. Moisten a pat of clay/inorganic silt slowly until it is saturated.
2. Shake the pat of soil in the palm of the hand; if it is inorganic silt, the pat expels enough water to make its surface appear glossy.
3. If the pat of organic silt is bent between the fingers, its surface becomes dull again.
4. After the pat of inorganic silt has dried, it is brittle and dust can be detached by rubbing it between the fingers.

Determination of hydraulic conductivity (k) for non-saturated soils

Inversed auger-hole method

The inversed auger-hole method consists of boring a hole to a given depth, filling it with water and measuring the rate of fall of the water level. By gradually deepening the hole and filling it with more water, the hydraulic conductivity (K) value of successive layers can be measured in the same hole. Test holes must be pre-soaked to obtain the more representative percolation rate for saturated soils. The hole should be made with minimum disturbance to the soil; the most appropriate augers are the open Dutch type for wet clay soils or the closed posthole auger for dry soils. Measurements should be repeated up to three times in loam or clay soils to give reliable results.

Method:

1. Dig an auger hole 1 m deep and fill it with water to saturate the surrounding soil (this takes ½ ­1 day).
2. Fix a peg near the hole with a horizontal strut as standard, and measure the distance between the standard and the bottom of the auger hole.
3. When the soil is saturated, fill the hole again with water to only 0.5 m of depth.
4. Place a measuring tape with a float attached to the end into the hole and measure the distance of the float to the standard at start, time t_l = 0.
5. Record time taken for the water level to fall by 1 cm (t₂, sec) and repeat 8 to 10 times at each 1 cm (or 0.5 cm) drop in level.
6. Repeat the test at a 2-m depth with water initially filled to 1.5 m.
7. Repeat the test at a 3-m depth with the water filled to 2.5 m.
8. Calculate K using the following formula:

   • K =  [1.15r log[h(t₁) + r/2] ­ log[h(t_n) + r/2]/t_n  ­  t₁ = 1.15r tan α

   where:

   K =	hydraulic conductivity (cm/sec)
   r =	radius of auger hole (cm)
   h (t1) =	water level in the hole at time t1 (cm)
   tn ­ t1 =	change in time (sec)
   h (t1) ­ htn =	change in water level over time (cm).

9. Plot h (t₁) + r/2 against t₁ to obtain a straight line with tangent α. Determine the K value from the graph where K = 1.15 tan α . Discard high initial values to obtain a lower K value than the one calculated using the formula. (See Figure E.2).
10. The K value of the soil should be less than 10 mm/day (< 0.00864 m/day or < 1 10^­5 cm/sec) if the soils are to be suitable for storing water.

Figure E.2. Graph of h (t₁) + r/2 versus t₁ in the calculation of K.

 

Example
Reading	t1 sec	h!(t1) cm	h(t1) cm	h(t1) + r/2 cm	t1 sec	h!(t1) cm	h(t1) cm	h(t1) + r/2 cm
1	0	73	17	19	0	71	19	21
2	40	74	16	18	140	72	18	20
3	80	75	15	17	300	73	17	19
4	150	76	14	16	500	74	16	18
5	250	77	13	15	650	75	15	17
6	350	78	12	14	900	76	14	16
7	550	79	11	13	1090	77	13	15
8	750	80	10	12	1300	78	12	14
9	975	81	9	11	1520	79	11	13

tan α₁= 2.0/10 x 1/1200 sec^­1
K= 1.15 x 4 x 0.000167 cm/sec  = 0.66 m/day

tan α₂= 2.7/ 10 x 1 / 2000 sec^{­ 1}
K= 1.15 x 4 x 0.000135 cm/sec = 0.54 m/day

(see Figures E.1 and E.2)

Slow sand filtration for water purification

Small-scale sand filtration is a method of treating water for consumption, which can be adopted in rural areas using locally available materials. As water slowly percolates through a bed of carefully arranged sand medium, almost all the suspended and colloidal material is trapped by the top layers of sand. Clear, filtered water is collected at the bottom of the filter medium. Besides sedimentation there is also some biological activity in a slow sand filter, with the growth of micro-organisms in the top layers of the sand. This microbial growth forms a sticky, gelatinous coat which increases the efficiency of the filter medium, provided that the filter is operated continuously. At a certain point the rate of filtration will become very low due to clogging, and the upper layer of sand should be removed for cleaning and then replaced.

A design of a simple sand filter for use in rural areas is shown in Figure F. 1. The container should be at least 1.3 m high and 0.5 m in diameter, and it can be made from oil drums, concrete rings or other available materials. A 20-cm layer of clean, round gravel of between 1.5 mm and 5.0 cm in diameter should be placed at the bottom of the container and covered by a 20-cm layer of clean coarse sand. The best sand has hard, round, durable grains free from dirt. Above the coarse sand should be at least 60 cm of fine sand with a grain size of 0.2 – 0.4 mm. Raw water should filter through the sand at a maximum rate of 1.5 litres per minute. This rate will be exceeded for the first couple of days, until the microbial activity becomes effective.

Figure F.1. A home-made, slow sand filter for water treatment.

The filter requires periodic maintenance at an interval varying from a few weeks to several months, depending on the water quality. The topmost layers of sand (5 – 10 cm) should be removed for cleaning, washed several times and then replaced to maintain the sand depth. Such a device will remove 97% of the bacteria, but it will not remove some of the smaller pathogens such as viruses. Water quality will nonetheless be significantly improved and the water will be much safer for human consumption.

Climatic data for 40 stations in Ethiopia

PE = potential evapotranspiration (mm) from Thornthwaite's formulae

T = temperature (°C); RF = rainfall (mm)

N = north latitude; m = elevation in m above sea level

Station		J	F	M	A	M	J	J	A	S	O	N	D	Total annual	Average annual
1.Gore	T	19.1	20.0	20.1	19.2	18.3	17.0	16.3	16.6	17.0	17.7	18.4	18.5	–	18.18
8°09' N	RF	39.5	46.9	111.2	136.8	259.5	417.1	334.2	332.2	327.4	191.6	97.2	74.9	2368.5
2002 m	PE	101.0	94.6	107.1	105.1	102.6	84.8	82.1	82.4	81.6	89.8	93.1	94.1	1118.3
2. Fiche	T	13.5	13.8	14.3	14.8	14.7	15.1	12.1	12.3	12.0	11.3	10.8	11.2	–	13.0
9°48' N	RF	11.9	20.1	72.4	67.3	46.6	64.0	497.3	407.3	143.4	35.2	6.7	9.5	1381.7
2820 m	PE	68.0	63.7	77.3	80.3	84.2	86.9	62.6	63.1	59.2	53.0	48.0	51.5	797.8
3. Wendo	T	16.8	18.4	19.0	18.3	18.0	17.3	17.1	17.3	17.5	17.2	17.1	16.9	–	17.6
6°35' N	RF	104.0	98.0	72.0	243.8	186.0	142.5	190.0	195.0	164.0	299.0	75.5	28.0	1797.8
1980 m	PE	80.6	86.5	102.0	94.9	95.4	85.5	85.9	87.2	84.8	83.4	80.2	81.6	1048.0
4. Gimbi	T	23.2	24.3	24.5	23.8	21.4	20.9	18.3	19.0	19.8	19.8	19.1	20.7	–	21.2
9°11' N	RF	26.8	0.0	35.7	105.7	271.1	359.5	302.8	402.1	394.3	99.1	11.2	9.4	2017.7
1870 m	PE	114.0	111.9	127.7	118.5	110.2	106.0	77.8	85.6	88.7	88.7	80.4	98.0	1207.5
5. Chencha	T	17.2	17.6	17.4	11.7	14.8	15.9	13.1	12.9	13.5	16.0	17.6	16.7	–	15.7
6°17' N	RF	84.0	41.8	194.1	205.5	215.7	141.0	129.1	91.2	117.9	221.1	41.8	39.1	1522.3
2700 m	PE	91.8	86.5	94.8	49.0	74.2	80.3	60.4	57.8	60.6	82.4	92.1	89.8	919.7
6. Debre Tabor	T	15.5	16.5	17.9	18.5	18.8	17.1	16.4	15.7	16.0	15.1	15.9	15.3	–	16.6
11°50' N	RF	8.4	14.8	40.7	50.2	98.2	212.9	486.2	485.5	193.0	48.8	14.8	5.4	1658.9
2945 m	PE	72.0	74.6	94.8	99.9	108.0	92.2	86.4	78.1	79.6	71.4	76.4	71.3	1004.7
7. DebreMarcos	T	15.5	16.5	17.3	15.9	14.2	14.4	13.2	13.2	14.1	13.2	13.4	13.3	–	14.5
10°21' N	RF	23.4	17.6	57.0	77.0	61.6	184.4	317.2	317.4	222.5	76.5	7.6	18.1	1380.3
2411 m	PE	78.0	77.4	94.8	82.4	71.3	72.1	64.8	64.2	67.3	61.2	60.8	61.4	851.7
8. Nekemte	T	17.5	18.5	18.8	19.4	17.9	16.8	15.4	17.1	18.0	19.2	20.0	20.7	–	18.3
9°05' N	RF	19.8	41.3	58.3	67.4	194.8	404.0	337.0	277.7	214.1	112.7	32.4	22.3	1781.8
2005 m	PE	85.0	84.6	99.9	105.1	95.1	83.7	70.2	85.6	89.8	103.0	101.9	106.9	1110.7
9. Megezez	T	7.7	6.7	6.7	7.0	7.0	7.6	6.5	7.1	7.2	5.6	6.0	6.1	–	6.8
9°15' N	RF	42.9	43:.0	90.6	41.4	36.5	78.0	197.3	209.1	138.2	11.8	13.3	13.3	915.4
3700 m	PE	56.0	44.6	50.5	52.5	60.5	59.4	51.8	54.6	53.0	43.9	44.1	44.6	615.5
10. Jimma	T	18.2	19.4	20.2	20.0	19.5	18.7	17.4	17.5	18.1	18.0	16.9	17.2	–	18.4
7°40' N	RF	28.0	31.3	105.6	184.8	194.6	241.9	219.2	237.8	179.0	51.0	26.2	38.9	1538.3
1740 m	PE	92.0	91.9	108.2	106.1	110.2	100.7	89.6	88.8	91.8	91.8	78.4	80.2	1129.7
11. Bonga	T	20.3	21.9	21.7	21.5	20.8	20.0	19.3	17.6	20.5	20.6	20.8	20.2	–	20.4
7°14' N	RF	57.1	66.9	148.4	179.4	243.8	198.1	175.6	181.8	188.8	143.3	56.3	47.2	1689.7
1720 m	PE	102.0	100.1	113.3	111.2	113.4	106.0	103.7	83.5	104.0	106.1	102.9	101.0	1247.2
12. Nejo	T	19.7	19.1	22.0	21.0	19.7	18.1	16.7	17.8	18.1	17.7	19.3	20.3	–	19.1
9°30' N	RF	3.4	10.2	14.6	73.7	164.4	227.9	284.0	303.6	306.7	149.9	11.3	11.8	1561.5
1850 m	PE	101.0	89.2	114.3	111.2	108.0	92.2	78.8	87.7	88.7	83.6	97.0	103.0	1154.7
13. Addis Ababa	T	15.7	16.9	17.9	17.7	18.0	16.7	15.3	15.2	15.6	15.8	15.3	15.3	–	16.3
9°02' N	RF	16.2	34.8	64.9	87.9	90.4	124.3	276.2	335.8	194.7	26.1	11.7	7.9	1270.9
2408 m	PE	750.0	774.0	948.0	948.0	994.0	890.0	77.8	77.0	76.5	76.5	70.6	71.3	980.3
14. Dangela	T	17.8	18.7	18.8	18.7	20.4	18.9	18.5	18.5	18.8	18.4	17.3	16.9	–	18.5
11°17' N	RF	3.7	30.3	10.4	48.9	92.6	193.4	379.6	301.0	236.0	153.8	10.0	9.0	1468.5
1981 m	PE	89.0	89.2	100.9	100.9	116.6	103.9	102.6	101.7	100.0	96.9	82.3	79.2	1163.2
15. Agaro	T	20.2	21.3	21.7	22.2	22.3	22.1	19.8	19.5	20.4	19.3	19.0	18.5	–	20.5
7º51' N	RF	39.0	31.1	89.5	103.3	158.8	234.2	223.7	274.1	209.4	123.7	32.7	31.6	1551.1
1500 m	PE	102.0	98.3	113.3	115.4	121.0	118.7	108.0	107.0	106.1	98.9	90.2	84.2	1263.1
16. Gidole	T	18.4	19.4	18.9	18.3	17.6	16.7	16.1	16.4	17.4	17.4	17.4	17.0	–	17.6
5°37' N	RF	38.0	47.3	175.3	131.0	199.5	53.0	204.7	107.7	68.2	161.6	53.8	0.6	1240.7
2550 m	PE	91.8	93.0	100.9	91.8	90.1	79.3	76.3	77.7	82.8	84.5	81.2	81.6	1031.0
17. Dilla	T	21.3	20.9	21.5	20.7	18.6	17.9	17.8	17.3	17.9	17.4	17.4	18.3	–	18.9
6°25' N	RF	80.9	12.1	132.0	150.0	133.7	136.6	91.8	144.7	184.2	207.3	44.9	34.3	1352.5
1635	PE	112.2	100.4	113.3	109.1	97.5	90.6	93.3	84.0	88.9	82.4	79.2	91.8	1142.7
18. Gonder	T	18.4	20.2	21.2	21.1	21.3	18.8	17.4	17.2	18.3	19.2	19.7	18.4	–	19.2
12°37' N	RF	2.2	15.5	16.7	55.1	70.8	188.4	332.5	353.6	140.4	46.9	46.4	19.8	1288.3
2120 m	PE	90.0	93.7	110.2	110.2	116.6	97.5	85.3	83.4	90.8	98.9	98.0	88.1	1162.7
19. Giyon	T	16.5	19.3	18.1	19.0	18.7	18.0	17.2	16.8	18.4	18.3	18.9	18.8	–	18.2
8°32' N	RF	20.4	27.3	60.3	74.9	47.9	181.2	257.7	349.3	106.3	89.6	0.0	1.0	1165.9
2007 m	PE	81.0	93.7	97.9	105.1	108.0	100.7	94.0	88.8	97.9	97.9	98.0	99.0	1162.0
20. Awasa	T	17.1	20.0	20.1	20.1	19.8	19.5	19.3	18.8	18.8	18.9	17.7	16.2	–	18.9
7°03' N	RF	14.0	43.0	186.0	187.0	112.0	75.0	181.0	75.0	128.0	90.0	57.0	6.0	1154.0
1760 m	PE	80.0	93.7	106.1	106.1	110.2	106.0	108.0	102.7	97.9	98.9	86.2	71.3	1167.1
21. Bako	T	19.3	21.5	21.2	22.2	20.4	19.7	18.4	18.8	18.7	18.8	19.1	19.0	–	19.8
9°07' N	RF	6.9	19.1	105.9	60.3	84.5	155.4	251.0	249.1	173.9	20.3	06.3	15.0	1147.7
1640 m	PE	96.0	100.1	111.2	118.5	113.4	106.0	95.0	95.2	90.8	90.8	94.1	94.1	1205.2
22. Kombolcha	T	16.6	18.1	19.7	20.1	21.0	23.0	20.5	20.4	19.5	18.0	16.8	16.3	–	19.2
11°04' N	RF	32.7	51.4	83.6	77.7	31.9	24.4	301.8	274.9	160.5	27.7	09.5	18.0	1094.1
1963 m	PE	72.0	81.0	103.0	106.1	116.6	125.1	114.5	113.4	100.0	90.8	70.6	69.3	1162.4
23. Dodola	T	12.5	14.4	13.7	14.5	13.7	13.1	12.4	13.8	12.1	11.8	11.2	11.9	–	12.9
6°58' N	RF	20.2	9.3	38.0	40.6	61.1	71.8	140.8	145.2	97.7	40.3	11.1	22.9	699.0
2540 m	PE	59.2	67.9	69.0	75.5	71.0	64.9	61.5	71.5	55.6	53.6	47.5	53.0	750.2
24. Gobba	T	11.6	12.4	13.5	13.1	13.5	13.5	13.5	13.1	13.0	12.1	11.6	11.1	–	12.6
7°01' N	RF	2.8	29.0	63.9	74.1	69.1	57.9	125.4	95.0	112.0	67.2	17.1	4.4	717.9
2743 m	PE	56.1	56.7	72.1	69.4	74.2	72.1	74.2	71.4	68.7	60.8	54.5	52.0	782.2
25. DebreBerhan	T	12.9	14.0	15.7	16.6	17.1	17.9	15.6	16.1	16.4	13.8	13.1	12.1	–	15.8
9°40' N	RF	22.8	8.0	31.4	27.2	36.5	24.5	293.3	269.7	78.3	1.8	6.5	8.0	808.0
2640 m	PE	56.0	59.2	81.4	90.6	97.2	103.9	84.2	87.7	87.7	65.3	56.8	49.5	919.5
26. Asosa	T	22.5	23.1	23.9	23.1	22.1	20.2	18.7	18.9	19.4	19.8	20.2	21.1	–	21.1
10°03' N	RF	0.0	5.0	4.0	89.3	76.3	111.3	220.7	203.9	210.6	116.0	8.0	15.4	1060.5
1640 m	PE	112.0	104.7	123.6	118.5	118.8	106.0	86.4	87.7	93.8	100.0	98.0	104.0	1253.5
27. Maychew	T	14.8	14.7	16.2	17.3	18.8	20.0	18.4	18.0	17.1	15.1	14.8	14.6	–	16.7
12°47' N	RF	18.6	20.4	67.5	83.9	38.8	12.3	205.9	242.6	84.7	30.0	5.2	7.7	817.6
2427 m	PE	66.0	60.1	82.4	90.6	109.1	111.3	103.7	101.7	88.7	71.4	64.7	64.4	1014.1
28. Sire	T	16.3	17.4	18.9	19.6	20.6	19.9	18.4	18.3	18.3	17.3	16.1	18.8	–	18.1
8°18' N	RF	8.5	9.9	63.0	71.1	28.5	70.5	157.8	182.3	193.0	97.3	1.3	3.7	886.9
1980 m	PE	72.0	75.5	97.9	104.0	115.6	109.2	99.4	98.4	93.8	84.7	69.6	94.1	1114.2
29. Mendida	T	20.5	21.5	22.5	22.6	21.4	19.6	18.3	18.5	19.2	19.2	19.3	19.5	–	20.2
9°39' N	RF	0.0	0.0	49.4	30.7	75.7	37.2	396.1	310.1	82.8	0.0	0.0	0.0	982.0
1650 m	PE	103.0	100.1	118.5	118.5	118.8	104.9	94.0	94.2	97.9	97.9	94.1	98.0	1239.9
30. Abella	T	20.6	20.7	21.3	21.3	20.4	20.3	19.9	19.4	19.9	19.8	19.8	19.3	–	20.2
6°52' N	RF	40.7	35.8	77.3	118.0	75.7	80.5	156.9	103.9	161.2	82.6	22.2	34.5	989.3
1675 m	PE	107.1	97.7	111.2	110.2	111.3	108.2	106.0	105.0	101.0	103.0	99.0	102.0	1261.7
31. Gambela	T	25.4	30.0	30.9	29.7	28.0	26.8	26.0	25.9	26.5	26.9	27.4	27.4	–	27.6
8°15' N	RF	3.6	14.7	26.5	76.8	157.4	178.3	233.1	310.0	204.3	105.4	44.0	15.7	1369.8
450 m	PE	130.0	147.2	172.0	164.8	159.8	146.3	140.4	139.1	137.7	141.8	140.1	141.6	1760.8
32. Burji	T	21.8	23.7	22.2	19.7	18.2	17.7	17.8	18.2	19.3	20.8	20.9	20.3	–	20.1
5°23' N	RF	39.3	32.6	109.0	148.3	130.5	37.0	56.4	25.5	76.5	157.2	36.2	38.6	887.1
1960 m	PE	112.2	111.6	115.4	97.9	90.1	82.4	84.8	89.3	96.0	108.2	104.0	105.1	1196.7
33. Kibre	T.	19.0	19.6	19.9	20.1	20.1	19.3	18.4	18.5	19.5	19.3	18.3	18.0	–	19.2
5°53' N	RF	21.4	30.5	84.0	201.9	102.1	56.5	48.3	60.3	55.3	168.0	49.7	14.1	892.1
1750 m	PE	97.9	94.9	105.1	107.1	111.3	103.0	97.5	96.6	103.0	103.0	91.1	89.8	1200.3
34. Koka	T	19.2	19.2	21.9	22.8	22.6	23.1	20.8	20.7	22.0	20.4	19.6	18.8	–	20.9
8°27' N	RF	17.5	21.2	47.1	61.1	46.4	58.0	223.8	209.8	110.3	29.3	9.1	13.5	847.1
1580 m	PE	92.0	83.7	113.3	118.5	124.2	124.0	111.2	110.2	112.2	104.0	95.1	87.1	1275.5
35. Wenji	T	16.6	19.8	22.7	22.9	23.3	23.2	21.0	20.9	21.2	19.5	18.4	18.6	–	20.7
8°20' N	RF	8.5	19.9	61.9	70.1	35.3	67.8	196.5	193.1	102.0	30.3	1.4	9.3	796.1
1540 m	PE	68.0	89.2	117.4	118.5	126.4	124.0	113.4	111.3	108.1	98.9	80.4	82.2	1237.8
36. Debre Zeit	T	17.5	18.7	19.9	20.8	20.9	19.7	17.9	18.5	18.3	17.7	16.9	17.4	–	18.6
8°44' N	RF	9.7	14.3	32.5	57.0	16.8	85.5	189.5	188.6	116.1	14.9	2.1	4.3	731.3
1850 m	PE	83.0	86.5	105.1	109.2	114.5	108.1	95.0	101.7	95.9	88.7	77.4	92.2	1157.3
37. Nazret	T	18.2	20.2	21.3	21.8	22.0	21.7	20.3	20.6	20.5	19.3	18.7	17.2	–	20.2
8°32' N	RF	0.0	0.0	9.3	13.5	45.5	73.5	163.6	212.3	160.5	45.5	0.0	0.0	723.7
1131 m	PE	87.0	93.7	113.3	114.3	110.2	117.7	111.2	111.3	106.1	98.9	87.2	76.2	1227.1
38. Mekele	T	16.2	17.8	19.2	20.8	21.2	21.1	18.3	17.7	18.7	18.2	16.9	16.1		18.5
13°31' N	RF	2.5	0.0	90.0	37.0	1.0	57.0	234.5	211.5	30.5	0.0	0.0	0.0	664.0
2130 m	PE	72.8	80.1	103.0	111.3	121.0	117.7	100.8	95.0	96.9	90.9	75.1	66.9	1131.5
39. Moyale	T	24.8	25.2	25.1	22.4	21.1	20.2	19.6	20.0	21.3	21.7	22.2	23.2	–	22.2
3°32' N	RF	7.5	9.7	53.5	227.3	87.4	9.8	9.2	18.0	9.8	148.5	101.0	43.0	724.7
1200 m	PE	124.4	117.2	129.8	111.2	107.1	94.8	90.1	94.5	103.0	108.2	105.9	116.3	1302.5
40. Asmara	T	13.4	12.6	15.2	15.4	17.0	17.2	16.0	16.4	16.7	15.5	14.5	14.2	–	15.3
15°20' N	RF	1.5	2.3	12.7	30.6	42.0	38.2	179.2	151.4	27.4	8.3	22.2	3.7	519.5
2349 m	PE	56.3	48.2	77.3	78.0	99.9	97.2	89.6	88.6	86.7	76.8	65.6	64.0	928.2

Source: Gamachu (1977).

Stations listed according to Thornthwaite's moisture regions with decreasing

moisture index (Im):

where:

Im = 100(S – D)/PE or 100 (r/PE – 1)

 S = annual water surplus; D = annual water deficit;

r = annual precipitation; PE = annual evapotranspiration.

Station	Climatic (moisture) region	Moisture index (Im)
1	Perhumid (A)	>100
2– 15	Humid (B)	20 – 100
16 – 25	Moist subhumid (C2)	0 – 20
26 – 40	Dry subhumid (C1)	– 33 – 0