cpwf pn 17 workshop, johannesburg, south africa 15-18 june 2009

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Biophysical and socio-economic factors affecting the use of in-situ water harvesting

technologies in the semi arid Limpopo Basin: Experiences from Gwanda district, Zimbabwe

CPWF PN 17 Workshop, Johannesburg, South Africa15-18 June 2009

I. Nyagumbo, M. Munamati, E. Chikwari and D. Gumbo Department of Soil Science and Agricultural Engineering

University of Zimbabwee-mail: inyagumbo@agric.uz.ac.zw

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1. Introduction

• In-situ water harvesting structures have been promoted in Southern Africa as a solution to drought mitigation in semi-arid regions and are an option to improved agricultural water management by resource constrained smallholder farmers.

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Increasing investment costs

Use of improved seed eg hybrids

Use of organic and inorganic fertilizers

In-situ water conservation & harvesting technologies

e.g. dead level contours, fanya juus, CAtied ridging/ furrows

Supplementary irrigation technologies

eg wetlands, surface irrigation

Hi- tech irrigation TechnsEg dripCostly

Upper limit for shf without capital

Options for improved agricultural water management

Options for improving green water productivity in rainfed systems

Options for bluewater productivity

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1. Introduction continued• In several situations the standard graded mechanical

conservation structures such as contour ridges have been found to be inappropriate due to excessive run-off disposal

• Promotion by NGOs and others particularly in Zimbabwe, has tended to be indescriminate i.e – All soil types (texture, soil depth)?– Topographic conditions?– Rainfall conditions?– All farmers?

• In Gwanda various organizations such as Practical Action, ORAP, ICRISAT and World Vision have promoted their use

• Not much is known about their effectiveness in terms of water conservation and drought mitigation. No hard data!

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1. Introduction continued

• However various options have developed in the last decade eg dead level contours with infiltration pits, fanya juus, deepened contours etc.

• The systems require extra labour compared to standard contours.

• Can we justify these huge labour investments by farmers!

• Could we probably fine tune recommendations for use of such structures?

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1. Fanya juu contour (Chivi, Zim)

• Structures placed at horizontal intervals of 20-30 m depending on slopes• Bank on upper side of slope• May be graded or on true contour

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2. Deepened contours can help to reduce the rate of disposal of excess water

Zvishavane, Southern Zimbabwe

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Contour bank

Infiltration pit

3. Infiltration Pits dug along a standard contour ridge channel

Buhera, Manicaland, Zimbabwe

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4. Dead level contours reinforced with covered infiltration pits

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Farmers believe covering the pits can help to reduce evaporation water losses!

But there is no quantitative data to support this view….!

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2. Study Objectives• To explore biophysical conditions (soil type,

depth, slope and topographic conditions) that characterise successful in-situ water harvesting

• To explore preconditions for success based on farmers experiences

• Refine recommendations for applying in-situ WH systems so as to justify scarce labour investments.

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3. Methodology

• Study carried out in Gwanda district of Zimbabwe (Mat South Province).

• Key partners: Gwanda Rural District Council, Practical Action, Agritex, students

• Studies carried out in Wards 17 & 18 of Gwanda district

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3. Methodology

• Meetings held at ward centres with farmers and community leaders– Key informants identified

• Farmers classified into 3 groups by own peers through group work by village– Very successful– Medium – Poor performers

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3. Methodology

1. Key informant survey: 14 respondents (general constraints and factors, information about users of in-situ WH farmers or respondents

2. Formal survey (55 respondents): socioeconomic characteristics

3. Biophysical survey: 14 sites investigated detailed soil studies of sites : Soil texture, depth, drainage, existence of impermeable bed rock, slopes

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Calculation of resource status• Respondents were classified into 3 resource categories

(wealthy, medium rich, resource constrained) based on 3 criteria

• Range of implement types• livestock value,• land size.

Livestock value • Market prices of livestock prevailing at time of study were used

in the formula (300D+250C+20G+5P)/575T where • figure is price in USD, • D = number of donkeys, C= number of cattle, G= number of goats, P=

number of poultry owned per hhd, • T is total price of individual livestock types

• Range of Implement types referred to the different types of implements owned

• The values from the 3 criteria were then used to classify the respondents into 3 groups.

3. Classification into Resource Categories

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3. Methodology cont’d

Relationships between performance of WHT and the following factors were investigated;– Sex– Resource status– Land size– Field location– Labour numbers– Age– Experience

• Data analysed using various SPSS statistical tools on the 55 respondents data

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4. RESULTS

Biophysical issues

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4.1 Perceptions of key informants on WHTs

Dead level contours with pits perceived to be most effective (72%)

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4.2 Location and Slopes of WHT fields• Field Location: 50% key informants considered

location as unimportant, 36 % =>homestead fields, 21 % =>far fields. Stats (N=55) showed insignificant correlation bwt success and location of fields. So location was not an important success factor!

• Slope did not seem to matter much (all slopes studied <4%) .However 64 % key informt farmers felt gentle to moderate slopes were prime. Stats based on a small sample of 14 analysed sites suggested slope was insignificant.

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4.3 Area of WHT fields and relationship with total arable area

• A significant linear relationship betwn total arable area and area under WHT (p = 0.000, r=0.84) , see figure below– The bigger the arable area the bigger the proportion put to

WHT

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Relationship between total arable area and that under WHTs (ha)

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• Resource status significantly influenced total arable area (p=0.000) and that put to WHT (p=0.001). Wealthy farmers had the highest total arable area followed by medium rich and lastly resource constrained farmers

• Avg area WHT=1.83 ha

• Avg total area= 4.49 ha

Resource status vs Total arable and Area under WHT

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4.4 Effects of soil typesFarmer class

Geology Soil texture Slope %

Soil depth (cm)

Soil depth limiting material

Inference

Highly successful

(N=7)

Mafic gneiss and dolerite

Coarse Sandy Loam to Sandy Clay loam / Sandy Clay (60 %)

<3 >70(71 %)

Slightly indurated (cemented) to moderately indurated in some cases(71%)

Deep soils hold more water . Limiting material causes bucket effect. Heavy texture enhancing water storage

Medium (N=3)

Mafic and siliceous gneiss

Predominantly Sandy Loam and some Sandy Clay loam(100% medium texture)

<2 <60 Moderately to slightly indurated

Medium texture close to surface. Shallow depth contributing to increased evaporation

Poor performers

(N=4)

Mafic gneissand granite

Loamy Sand to Sandy Loam on surfaces, Sandy Clay Loam in subsoils

<2 <60(100% shallow)

Well to moderately indurated, some slightly indurated

Excessive water loss by evaporation due to shallowness. Light texture not holding much water

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4.4 Effects of Soil types • Most of the best farmers had heavier textured soils

while the poor farmers had light textured soils. 83 % of the respondents key inf. felt deep soils were more effective.

• Shallow depth <60 cm also characterized the poor performers while deep soils >70 cm were more apparent among successful farmers.

N.B.The existence of a slightly indurated parent material seems to enhance the bucket effect but at the same time allowing drainage to take place in excessively wet periods!

Socio-economic issues

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• Generally there is significant correlation between performance and resource status, at p=0.004

• Within the wealthy category,42.1% are successful, while 14.3% and 13.8% are average and poor performers respectively

• Within the medium rich category, the majority were average performers(57.1%) compared to 42.1% and 34.1% successful and poor performers respectively

– Reason; innovative, capitalise on new opportunities to acquire knowledge and other resources accessible within the community

• Within the resource constrained category, the majority (75.0% ) were poor performers

– Results suggest that wealth status contributes to success or failure in use of WHT

– Medium wealthy people could be best bet investment targets for technology! Drivers of change

4.5 Resource status vs Perfomance

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Sex vs Perfomance• Performance rating was

significantly correlated (p=0.007) to sex of household head.

• Eg Within the most successful group 94.7 % were men compared to 5.3 % women

• In the average performance category, 71.4% men and 28.6% women

• Within sex, 82.4% of women were poor performers compared to 17.6 % in the other categoriess. Only 39.5% men were in the poor cat.

4.6 Links between performance and sex

N.B Widows, hhd with absent husbands disadvantaged, targeting?

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Sex vs Resource status• Sig Pearson correlation

between resource status and sex (p=0.039).

• Within the wealthy category, 69.2% of respondents were men compared to 30.8% women.

• In the medium rich category 86.4 % were men compared to 13.6% women.

• Within sex category most women (58.8%) were resource constrained compared to men (26.3%)

4.7 Correlation btw sex and resource status

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Experience vs Perfomance

• No significant difference in mean years of experience across performance ratings,– Although data tended to

show a decline in performance with decrease in number of years.

– Increasing experience also tended to reflect increase in performance

4.8 Does experience have anything to do with performance?

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4.9 Labour and resource status/ performance

• No significant difference between labour numbers and performance and resource status. Avg per household=6.3 (n=55). However, the majority (93% KI) of the farmers felt labour was a key factor for success.

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4.10 Other issues• The most successful farmers had made

modifications to their systems which included: plastering the bottom of pits, covering the pits to reduce evaporation, altering the depth etc.

• Education and social status did not have any bearing on performance

• A sig. difference (p<0.05) in age between successful and poor performers with the elderly being more successful.

• Average age was 51 years

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5. Any Conclusions?

• Performance of WHTs dependent on soil type:– Best performance is obtainable from deep, heavy

textured soils with some underlying semi-permeable bedrock

• There was no apparent preference in allocation of land for WHTs between homestead and far fields.

• Slope had no apparent effects but could be because study area had limited slope ranges

• The proportion of land under WHTs increased with land ownership and so well resource farmers had more choices.

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5. Conclusions• Resource ownership could be a key factor in farmers ability to scale out WHTs. Performance was

significantly linked to resource status.• Medium wealthy people could be best bet investment targets for technology! • Women headed households were performing rather poorly in WHTs suggesting the need for special

attention to gender in the promotion of WHTs

• The influence of labour on performance was not apparent from the study (methodological limitations!)

• Resource ownership could be a key factor in farmers ability to scale out WHTs. Performance was significantly linked to resource status.

• Women headed households were performing rather poorly in WHTs suggesting the need for special attention to gender in the promotion of WHTs

• Sex, labour and land size are also key factors

• Performance of WHTs dependent on soil type:

• Best performance is obtainable from deep, heavy textured soils with some underlying semi-permeable bedrock

• Study area had limited slopes and so slope had no apparent effects

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6. Next Step!

• Use of GIS tools and Remotely sensed data to assess historical performance of WHTs still to be done but limited by resources

• There is need for more resources for more in-depth studies to demystify performance variation across locations and conditions particularly in Phase 2!

• Department has the zeal!

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Thanks!!