Contrasting Local and Basin Perspectives On Artifical Recharge

The existence of more than 250,000 tanks and ponds in hard-rock-covered areas of peninsular India itself shows the importance accorded by agriculturalists and rulers for managing the surface water sources locally. However, most of the tanks are old and their storage capacity has reduced due to siltation, and recharge volume of

Table 10.1. Economics of various artificial recharge methods. (From UNEP International Environment Centre, 2004.)

Capital cost/1000 m3 Operational cost/ Artificial recharge structure type of recharge structure ($) 1000 m3/year ($)

Table 10.1. Economics of various artificial recharge methods. (From UNEP International Environment Centre, 2004.)

Capital cost/1000 m3 Operational cost/ Artificial recharge structure type of recharge structure ($) 1000 m3/year ($)

Injection well (alluvial area)

551

21

Injection well (hard-rock area)

2

5

Spreading channel (alluvial area)

8

20

Recharge pit (alluvial area)

515

2

Recharge pond or percolation pond

1

1

(alluvial area)

Percolation tank (hard-rock area)

5

1

Check dam

1

1

water through the tanks has been considerably reduced. At the same time, the tank command areas have increasingly been put to multiseason cropping use with higher cropping intensities than they were originally designed to meet. As a result, farmers have turned in increasing numbers to the utilization of groundwater through dug and bore wells. The increase in the extraction of the limited renewable groundwater resources has led to a decline in water tables, especially in areas where density of wells is high and rainfall is moderate to low. This in turn has provided the impetus for the groundwater recharge movement.

As briefly discussed, there have been many studies on artificial groundwater recharge that have shown its technical effectiveness. In Maharashtra, it was shown that when tank bottoms were maintained by removing accumulated sediment and debris prior to the annual monsoon, the average recharge volume was 50% of the capacity of the tank (Muralidharan and Athavale, 1998). In Tamil Nadu and Kerala, studies carried out by CGWB on nine percolation tanks in the semi-arid regions of the Noyyal, Ponani and Vattamalai river basins showed that percolation rates were as high as 163 mm/day at the beginning of the rainy season, but diminished thereafter mainly due to the accumulation of silt at the bottom of the tanks (Raju, 1998). In Punjab, studies of artificial recharge using injection wells were carried out in the Ghagger River basin, where using canal water as the primary surface water source showed that the recharge rate from pressure injection was ten times that of gravity systems and that maintenance was required to preserve efficiency (Muralidharan and Athavale, 1998). In Gujarat, studies of artificial recharge were carried out that showed a recharge rate of 260 m3/day with an infiltration rate of 17 cm/h (Phadtare et a/., 1982).

Local level benefits of groundwater recharge in Gujarat

Why artificial recharge is growing in popularity can be seen from an example from India's arid western region. The year 2000 was an unprecedented drought year in Gujarat. The water crisis that year had created an intense awakening among the people of the Saurashtra and Kutch regions about the importance of water. Social workers and NGOs undertook numerous water-harvesting projects to recharge groundwater for domestic and agricultural uses. These projects were often funded by voluntary contributions from affected people. Because of the apparent success of these efforts, under the Sardar Patel Participatory Water Conservation Programme (SPPWCP), the government of Gujarat invested more than Rs 1180 ($28) million in construction of more than 10,000 check dams across Saurashtra, Kutch, Ahmedabad and Sabarkantha regions in 2000/01, which was co-financed by beneficiary contributions. Overall, 60% of the funds was supplied by the government and 40% by direct stakeholders. The responsibility for managing the quality of construction works fell to beneficiary groups and NGOs.

An independent evaluation of the check dams in Gujarat was carried out in 2002 by the Indian Institute of Management (IIM), Ahmedabad, which covered vital aspects of the project including advantages of people's participation and impacts on agricultural production, drinking water supply and availability of fodder as well as overall socio-economic cost-benefit analysis (Shingi and Asopa, 2002).

From the analysis of survey data covering over 100 check dams, personal visits by the evaluation team to a large number of other check dams and interviews with more than 500 farmers, the team concluded that:

1. Localized rainwater harvesting systems in the form of check dams in Saurashtra were an effective solution to the water crisis through their ability to channel rainfall runoff into the underground aquifer. This offered a decentralized system for decreasing the impact of drought and allowed the people's involvement in critical water management tasks with simple, local skill-based, cost-effective and environment-friendly technologies.

2. The rainwater harvesting efforts initiated with people's participation and support from SPPWCP should be relaunched and reimplemented on a larger scale.

3. The 60:40 scheme (60% by government and 40% by beneficiaries) had six major features capable of attracting donor investment: (i) ecologically sound principles behind the concept; (ii) highly participatory nature of the programme, which allowed beneficiaries to contribute their share of the investment through labour, equipment and/or money; (iii) gendered nature of the outcome in that women were the major beneficiaries of the alleviation of drinking water and livestock feed problems; (iv) the fact that the project did not replace or endanger human or wildlife habitat; (v) focus on equitably using renewable resource like rainwater; and (vi) economic and financially sound nature of the work and its short payback period.

4. The 60:40 scheme has been, and should continue to remain, a people's programme, and it is unlikely to survive otherwise. It is felt that only the people's involvement would ensure the survival of critical components like (i) quality of works; (ii) prevention of undesirable contractor's entry into partnership with government; (iii) sustainable maintenance and supervision; (iv) speed of implementation; (v) ingenuity and innovation in implementation; and (vi) cost-efficient technical guidance.

Basin-level costs of groundwater recharge in Gujarat

Some believe that local efforts to increase artificial recharge account for only a small fraction of the massive amount of rainfall on the vast area of any particular catchment or basin. As a result of this thinking, artificial recharge by scattered local communities will not have a perceptible impact on downstream flows or impact downstream surface or groundwater users. However, from a basin perspective, all water use is likely to have some impact on users elsewhere in the system. These impacts are likely to be greatest when basins are 'closed' (i.e. all available supplies have been fully allocated) and in cases with marked inter- and intra-annual variation in rainfall. These are precisely the places and conditions under which groundwater recharge is likely to have the largest local appeal. The potential problems behind this issue are brought out by the following example, which is also from Gujarat.

The watershed known as Aji1 in the Saurashtra region of Gujarat is considered water-scarce and closed, and has high variation in rainfall ranging from

Fig. 10.1. Rainfall and runoff variations in Aji1 watershed from 1968 to 2000.

Fig. 10.1. Rainfall and runoff variations in Aji1 watershed from 1968 to 2000.

200 to 1100 mm/year. Aji1 reservoir supplies water to the city of Rajkot, located at the downstream end of the watershed. Starting around 1985, the flow to the reservoir began to decline sharply. It was hypothesized that the decline was caused by the construction of thousands of check dams and percolation ponds within the watershed, the result of a recharge movement initiated by Shri Panduranga Athavale, a religious Guru of Saurashtra, and later supported by the government of Gujarat.

In order to verify whether the decrease in flow into the downstream reservoir was related to the proliferation of upstream check dams and percolation ponds constructed to recharge the groundwater aquifer, rainfall and inflow data to the reservoir was collected for the years 1968-2000 and a simple analysis was made to compute the runoff coefficient as shown in Fig. 10.1. Although rainfall remained approximately the same throughout the period, the runoff coefficient declined markedly, especially after 1985 when the recharge movement reached its full impact. The average reduction in the runoff coefficient after 1985, almost to half of its original value, suggests the extent of the impact the upstream water-harvesting structures had on the downstream reservoir. While the impact of upstream artificial recharge on downstream users in other basins may differ from this example, what is clear is that there will be an impact (Molden and Sakthivadivel, 1999).

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