Jaime E. Díaz Ortiz¹ y Carlos Alfredo Ramírez²

¹Agricultural Engineer, Universidad del Valle, Cali Colombia. M.Sc., in Water Resources, Universidad Nacional de Colombia, Colombia. Ph.D., Agricultural Engineering, Universidad Politécnica de Madrid, Spain. Universidad del Valle. jaidiaz@univalle.edu.co.

²Agricultural Engineer, Universidad del Valle, Cali Colombia. Colpozos S.A. carlosalfredo24@hotmail.com

ABSTRACT

The infrastructure for small irrigation systems demands costly investment which may become increased as many social and technical aspects related to the concerns of regions susceptible to investment remain unknown. The lack of both information and a social network supporting planning and design tasks constitute factors affecting many irrigation projects, consigning them to failure. Some indicators were prepared for constructing an irrigation system in the north of the Cauca department in Colombia which, in turn, led to determining investment priorities and facilitated decisionmaking. The indicators guaranteed that the construction would benefit the greatest number of users, assuring wider irrigation coverage. The project lasted forty-two months; the basic irrigation system was designed and constructed during this time, alternating direct reception via surface water sources and digging wells to use groundwater. Investment costs were lower than estimated FAO reference ones.

Keywords: irrigation-water, basic irrigation system, watermanagement.

Received: june 3th 2009

Accepted: november 15th 2010

Introduction

Developing infrastructure in traditionally-depressed regions is a complex issue, due to growing financial pressure and the communities' weakness in seizing the opportunity offered by technological advances benefitting themselves. Increased efficiency in the investment management requires planners, designers and infrastructurebuilders for social and economic objectives to develop methodogies facilitating the selection of alternatives offering higher returns and greater coverage.

An irrigation water distribution system rewires complex infrastructure consisting of intake, transmission, distribution and regulation structures, allowing water delivery to users in an efficient and time ly manner.

Physiographic, hydrological, climatic, agronomic, social and economic needs for small irrigation projects are quite heterogeneous and scant information is available about or for them. It is thus difficult for system planners and designers to make good decisions, due to a lack of sufficient and reliable information (FAO, 2006).

According to Cárdenas (1978), officials and representatives involved in water management in developing countries, in most cases, are urged to offer alternative solutions for irrigation water allocation problems, resulting in inadequate planning reducing allocation efficiency. In some situations, a lack of time, experience in strategic planning or lack of knowledge for transferring management experience leads to unfortunate decisions being made. Ostrom (1999) stated that it is often observed that state intervention on some occasions does not serve to maintain and strengthen its own management ability and contributes towards organisational collapse, hampering its creation or correct functioning.

Investment in irrigation infrastructure around the world began during the last century and has become increased since then; however, the results, in most cases, have not reflected an appropriate response to expectations and investment costs. Kijne et al., (1998),have evaluated several irrigation projects and identified some negative impacts; one of the most notorious was soil salinity caused by inadequate water management.

Analysing the problems caused by inadequate water resource management has led to concluding that a committed community can provide elements contributing towards more efficient irrigation system construction and management. Bandaragoda and Memon (1997) have mentioned that the absence of written records and regulations hinders the development of indicators, complicating the tasks of monitoring and evaluating small irrigation systems. Methods based on participatory irrigation management involving water-users in irrigation management have contributed towards improving water management and increased efficiency (Vermillion and Sagardoy, 2001).

Martínez and Palerm (1997) consider that most self-management organisations for managing, maintaining and constructing irrigation systems do not have the discipline to write regulations specifying activities or maintenance, water distribution, conflict resolution, supervision, monitoring and electing administrative people.

Constructing agricultural indicators has traditionally been used for identifying strategies for operating irrigation systems and determining whether they are sustainable in years of water shortage. The indicators are useful for comparing different plots; however, they are not therefore used for simultaneously comparing locations having different contexts. It is more convenient to take fewer units and set ranges according to similar criteria (size, dominant production structure, diversified water use, etc.) to offer a signify-cant diagnosis.

A good indicator should provide data on many aspects, specifically for irrigation. Vermillion and Sagardoy (2001) have shown methodologies developed with indicators measuring the impact of investment on regional economies' growth, increased water supply and strengthening community organisations. Mock and Bolton (1993), Hammond et al., (1995) and Garcés and Guerra (1999) have developed environmental indicators showing the impact produced by constructing irrigation systems. Rymshaw (1998) developed indicators in some Mexican districts, looking at patterns for maximising profits generated by land and water resources. Supply indicators comparing drought averages in 14-year series can lead to longterm performance standards being set when there are severe water restrictions per area. Indicators based on analytical assessment related to yield, crop quality, maintaining soil production capacity and environmental protection have been developed for determining water quality for agriculture.

These indicators have been produced from the physical, chemical and microbiological elements involved in the relationship between water and soil. Some of the proposed methodologies provide only qualitative comparisons without providing conclusive final results (Lacoste, 1997). One possible way of addressing this problem is to use simple numerical scales related to the degree of contamination (Beron, 1984).

The International Water Management Institute (IWMI) has designned a set of nine indicators for comparing irrigation system performance, based on work done by Perry (1995) and De Fraiture and Garcés (1998). The parameters are based on two aspects: one referring to agricultural production and the other to water use. The first is based on determining irrigation intensity and the relationship between gross production values per hectare and the control area, the irrigated area, the volume of production per water unit supplied and per water unit consumed The second refers to water availability, irrigation availability and water delivery capacity.

Bos and Chambouleyron (1999) proposed some performance parameters for comparing and correcting inefficiency in agricultural land management and irrigation management in the province of Mendoza (Argentina); some of them emphasise a special administrative model. A number of indicators for evaluating irrigation systems have been implemented in Latin-America; they can be classified into three groups: agricultural (physical, economic, environmental), management (administrative, financial, social) and irrigation network operation. The latter specifically relates to identifying efficient types of water management (Maldonado, 2000).

Irrigation performance can be evaluated for various purposes intended to help irrigation managers and water users' organisations to improve water supply services for farmers. The typical indicator used for this purpose relates actual accomplishment with standards established by irrigation managers. Many indicators have been used for improving individual systems' management and organisation (Bos et al., 1999, Murray-Rust and Snellen, 1993).

Vermillion and Garcés (1998) considered that the indicators most commonly used in irrigation are related to irrigation system staff reorganisation, reduced government expenditure on operation and maintenance, irrigation costs for farmers, changes in irrigation system budgets, banking fees and costs and irrigation in-frastructure functional status.

Indicators helping decision-making in system management are related to net present value (NPV), internal rate of return (IRR) and benefit/cost (Conpes, 2005). Vermillion and Sagardoy (2001) have proposed indicators for assessing irrigation system impact and even for use in making construction decisions. The variables considered were: irrigated area served, water supply quality, irrigation efficiency, agricultural productivity and cost per unit of land and water, farm incomes and job creation, area affected by water-logging and/or salinity.

As noted, there is no criteria for facilitating decision-making concerning priority investment in traditionally-depressed areas. Cultural, social, legal parameters and technical standards were analysed for this project; they were used for developing qualitative and quantitative indicators facilitating the selection of properties having the best potential for investment in basic irrigation systems. The project benefited rural farm families in the municipalities of Padilla, Puerto Tejada, Guachené, Villarica and Miranda.

Methodology

The Natural Resources and Environmental Engineering School (Universidad del Valle, Colombia) conducted a four-year project in the north of the Cauca department to improve the technological basis for regional agricultural production. The basic irrigation infrastructure for Afro-descendant and mixed-race land owners or tenants was designed and built during this time; these people cultivate traditional products like cocoa, banana and fruit. The population's cultural conditions are fairly homogeneous, being characterised by their low educational level, low organisational level and lack of interest in participating in community projects.

The agricultural region is formed by a combination of different land tenure systems; scattered small-scale subsistence farms involved in minimum agriculture having little or low technological development regarding their infrastructure and large farms run by companies involved in agricultural development whose production is based on the large-scale use of technology supported by large-scale capital investment.

Prospective users' investment potential was initially identified. This information was systematised by using digital mapping of the area (1:25000 scale, IGAC, 1989). A detailed thematic map of the study area was then constructed based on such information. Geospatial information was then added, consisting of the following components: towns and roads, surface hydrology (rivers and streams), a meteorological station network, variation in aquifers' specific capacity, location of the land being benefited and the basic infrastructure of premises connected to the mains and housing.

Sub-basins and watersheds were delimited to calculate runoff contributing to surface water sources. Those having the best potential for irrigation use were located and selected. Variations in flow during periods of drought and non-drought were studied. Information from the network of meteorological stations in the a-rea facilitated calculation of supply from water-demand for agricultural alternatives. Global positioning systems (GPS) were used for locating farms participating in the project; such information was tested on the water supply plan to determine spatial distribution and distances between surface water sources and farms. The specific flow curve helped identify groundwater potential in the area and its distribution in the subsurface.

Sources of supply and hydraulic designs were defined for the network for all supplying potential plots using EPANET software (US Environmental Protection Agency's Water Supply and Water Resources Division, version 2.0), simulating different water scenarios. Diameters were selected for distribution networks having more than 40 mca pressure at delivery points, facilitating the installation of high frequency drip irrigation (Walker, 1989). Specific flow curves led to selecting farms having the most potential for groundwater exploitation, providing alternative uses with shallow well construction which were programmed as individual or collective solutions, depending on the density of premises.

Total investment cost was quantified with the final designs for irrigation construction infrastructure in all potential properties being benefited, regardless of supply source. A methodology was defined for facilitating final selection that involved cultural, social, legal and technical variations. The model was based on evaluating the variables, allowing properties having the highest scores to be chosen, according to established weighting. Cultural, social and legal variables were based on plot density, the number of beneficiaries having collective solutions prioritised above individual solutions, the degree of user involvement in the socialisation workshops held to plan the project and the network paths. Legal and fiscal status was considered relevant, assessing compliance with tax obligations as a sign of social and financial responsibility. Values were measured with 40% weightin and are presented in Table 1.

Technical variables took into account the availability of on-site power supply, the existence of housing to ensure protection of investment, ease of vehicle access to farm to facilitate construction work, the distance to the water supply source and farm location in areas having specific capacity curves above 3 l / sm values (60% weighting) (Table 2).

Users were scored by implementing the above criteria. Project costs were used for developing quantitative indicators definitively stating the selected beneficiaries. The indicators were estimated using variables related to investment cost per property and the average of all beneficiaries, recovery of project cost and costs per hectare. Indicators were defined as follows:

- IN₁= Investment per beneficiary / average investment per bene-ficiary

- IN₂= Investment per hectare / per hectare exploitation of the project area

- IN₃=Investment per hectare / average investment per hectare.

The sum of the product of the indicators by weighting factor (FP) determined the overall indicator (IT), which was applied to the users to determine final beneficiaries.

Results and Discussion

The relationships established by qualitative and quantitative indicators were determined to start civic construction for participation in civil society to initiate a desire for owning their own destiny. Financial investment was evaluated for the efficient use of resources which are always scarce; this was intended to generate an impact prioritising community solutions over individual interests.

An indicator score lower than 1 (IT < 1) was considered to be a viable solution, thus ensuring that selected properties had a greater return on investment. This limit was set considering that IIWA provides a similar approach, based on the ratio between the to-tal water volume supplied by rainfall and irrigation to an area based on crop water demand, indicating that water demand is satisfied when the ratio is below 1.

Final selection meant that selected users not only met a number of legal and technical requirements, but also that their properties had the best benefit-cost investment and that resources allocated to the project had the widest possible coverage.

Eighty-four final beneficiaries were identified, based on applying qualitative and quantitative criteria, having an indicator total (IT) less than 1. The selected farms were divided into two groups: one, consisting of 46 solutions, was supplied directly by surface water sources and the other 38 solutions involved tapping underground water supplies (medium depth wells were constructed). Basic water supply systems were built for each property for all solutions, thereby allowing maximum use of available financial resources.

Total investment was US$ 780,974 for a total area of 84 hectares. Average cost per hectare for the entire project was US$ 3,197.

Differentiating the investment by type of solution provided, it was found that average investment was US$ 1,733 / ha for pro-perties having direct supply and $ 4,389 / ha for farms with groundwater wells. These values were lower than investment costs regarding US$8,000 / ha irrigation infrastructure cited by Kloezen and Garcés (1997). It should be noted that investment was only made for constructing basic infrastructure, regardless of irrigation equipment cost. Even including these costs, investment per hectare was still below estimatedcosts for this type of project.

Conclusions

The methodology allowed likely project beneficiaries to be classified, leading to 84 recipients being selected who met estimated indicators' parameters.

The selected farms had an average US$ 1,733 investment per hectare for direct solutions and US$ 4,389 for solutions involving wells (lower values than those estimated by FAO for this type of project).

The quantitative benefits obtained by the community in the project included civil society participation and strengthening solidarity bonds for developing such projects.

This study has presented an initial proposal for constructing indicators for selecting investment alternatives for construction projects involving basic irrigation systems taking the study area's particular characteristics into account. A community of about 84 families in an area of 84 hectares benefited from this particular initiative