Introduction

The Western Ghats of southern India act as a water tower (Viviroli et al 2007; Fisher 2018) for adjacent foothill areas and provide a crucial recharge area for groundwaters. They are also important in delineating the scale, location, onset, and variation of the southwesterly Indian monsoon for southern India. Unfortunately, water scarcity has become a major concern in southern India because of a complex array of pressures. Population increases (Cincotta et al 2000; Jain 2011) and climate changes (IPCC 2014; Kattumuri et al 2017; Fukushima et al 2019), such as the delay of monsoon onset (Kripalani et al 2007) and periods of drought and flood, result in a decrease in crops (Krishna Kumar et al 2011; Kumar et al 2011) and forest productivity (Chaturvedi et al 2011) and cause seasonal water scarcity (Jain 2011). Thus, there is a call for an increased focus on traditional water-harvesting techniques on the Indian subcontinent (Kokkal 2002; Agarwal and Narain 2005; Jacob 2008), due in part to their greater sustainability in comparison to large-scale irrigation systems (Christensen 1998) and their ability at times to provide drinking water. Only 28% of the rural population have access to an official drinking water supply, which is below the national average of 67% (Aayog 2018). Those without these supplies are reliant on buying water or finding sources outside of government supplies. This is the situation in southern Karnataka and northern Kerala. According to the Centre for Water Resources Development and Management, groundwater resources are overexploited in the district of Kasaragod in Kerala (Kokkal 2002; Balakrishnan and Saritha 2007), while the Central Groundwater Board notes that Dakshin Kannada in Karnataka regularly experiences a groundwater resource crisis (Dhiman 2012; Ramaiah et al 2017), which disproportionally impacts small farmers (Anantha 2013). In response to this water crisis, the neighboring state of Kerala introduced a Ground Water (Control and Regulation) Act in 2002, and Karnataka introduced the Ground Water (regulation and control of development and management) Act in 2011. Thus, at a local level in southern Karnataka and northern Kerala, farmers face choices about how best to conserve groundwater depending on the topography and geography of their farm unit. These decisions are predicated on their past experiences of water shortage with regular drought periods of 5–9 years in the region (Amrit et al 2018). At an individual farm level, as well as worries over water scarcity, farmers must face up to political and economic vacillation that potentially impacts the security of land tenure and leaves them regularly facing uncertain market and labor availability conditions (Balooni et al 2010). This makes individual investment in water-saving technology unlikely and water-saving initiatives run by water companies and local governments hard to implement. Thus, local adaptive responses to water scarcity assume a heightened level of importance. One local response to this issue of water scarcity, first implemented around 100 to 150 years ago, was to construct smallholdings on excavated slope terraces supported by a little-known technology defined as a gallery filtration tunnel irrigation system called suranga (Crook et al 2015). Suranga are well suited to the undulating and steeply sloped terrain of the foothills of the Western Ghats. This paper provides the first comprehensive outline of the design principles of the suranga water-harvesting system.

Study area

The foothills of the Western Ghats are characterized by relatively low, but at times steep, terrain, with a series of rounded hillocks (Kale 2009) that create a landscape characteristic of a remote upland area (Vincent 1995). This exploratory study was carried out in the districts of Dakshin Kannada in Karnataka State and Kasaragod in Kerala between 2012 and 2014 (Figure 1). The population of the Dakshin Kannada district at the time of the last census was 2,083,625 with a density of 457 people per km²; in Kasaragod it was 1,307,375 with a density of 604 people per km² (ORGCCI 2011). Most people in this region live in rural locations and engage in a mix of subsistence and small-scale commercial farming; for the latter, most rely on producing plantation crops, such as areca nut and rubber. The climate is characterized by high humidity (78%) for the greater part of the year. There are four seasons: June to September when the monsoon occurs, October to November, which is warm and damp, December to February, which is cool and largely dry, and March to May, which is dry with rising temperatures. The average annual rainfall in the Western Ghats is 3000 mm (Dhiman 2012), although rainfall over the 6000 mm isohyet characterizes the escarpment continuing down into Kerala (Putty et al 2000; Putty and Yadupathi 2006). Around 85% of the rainfall occurs during the southwest monsoon (Dhiman 2012). The capacity of soils to absorb or store water is thus important in ensuring reliable year-round water availability for farmers. The tropical and monsoonal climate is responsible for laterite soil profiles (Persons 1970) that are a residual deposit characteristic of the region, produced by intense weathering.

FIGURE 1

The study area: Dakshin Kannada (Karnataka) and Kasaragod (Kerala). (Map by authors, based on Google Maps India)

Research methods

Using a snowball survey technique, started by liaising with one key gatekeeper, 215 households were interviewed to contribute to an inventory revealing suranga systems in Dakshin Kannada and Kasaragod (∼720 km²). These farmers were interviewed over 2 field seasons, in 2012 and 2013, but regular discussions with the gatekeeper have been maintained up to present. The main language and culture of the villages surveyed is Kannada, but Tulu is also widely spoken. A translator/facilitator was employed to facilitate access to family testimonies and their farm units. Interviews were also used to collect information about the state of water resources and socioeconomic status (scheduled caste/tribal group) determined according to where families fell above or below the poverty line. The social survey was approved by the University of Hertfordshire School of Life Sciences ethics committee, and the protocol number issued was LS5/7/12SR.

To better understand the provenance of different underground water sources, a suite of 8 range-finder ¹⁴C accelerator mass spectrometry dates were collected to estimate the residence time of water, allowing us to infer the source of the groundwater. The equivalent “apparent” radiocarbon age to the reported percent modern carbon (pMC)/fraction of modern (fMDN) values were analyzed by Beta Analytic on 6 November 2013 and 2 November 2014. These results allow us to infer the speed of recharge of different groundwater sources, which in turn allows some assessment of the suranga systems’ vulnerability and resilience to climate change. The second objective was to conduct a survey of suranga discharges over the postmonsoon (September–November 2012) and premonsoon (April–May 2013) periods to account for seasonal differences in water availability. Discharges from several accessible suranga in Manila village (12°41′22.12″N; 75°4′50.67″E) were considered representative of all the suranga surveyed based on their size and flow regimes. These were calculated using a volumetric technique because of the low flows found in most suranga conveyance channels (Kokkal and Aswathy 2009). These discharge measurements were taken on 3 separate occasions to find an average discharge figure. Discharge measurements were also taken monthly over 2 calendar years to account for seasonality.

Results

Socioeconomic effects

Suranga were defined as a gallery filtration tunnel system dependent on groundwater recharge found mainly on sloping terrain with laterite soils (Figure 2). We counted 700 suranga, which when added to existing partial inventories (Kokkal 2002; Kokkal and Aswathy 2009; Balooni et al 2010) gives an overall figure of at least 3000 suranga predominantly in the areas of Dakshin Kannada and Kasaragod. At least 2 extensions of the system had been created by the transfer of the technology to Shivamogga District in northern Karnataka and Ponda in Goa. There is a large amount of evidence for the use of multiple suranga systems on a farm to exploit different microcatchment dynamics (Crook et al 2016). Water supplies from traditional systems, which include suranga as a key component, often have a cascading system of hydrological connectivity linked to the use of farm ponds and dug or stepped wells. Crop choices are not influenced by the delivery technology. The system is dynamic, featuring both new construction and abandonment. The percentage of suranga found in our survey to have been abandoned as a result of partial collapse or drying up was 18%. Suranga are constructed by individual landowners or sometimes by a tenant such that the water rights attached to these are riparian. There is no official regulation of the construction and number of suranga on a property. This decision falls squarely on the landowner. It was discovered through multiple correspondence analysis (MCA) of the survey data that suranga ownership was almost equally associated with families below and above the poverty line. Poor families may dig the tunnel themselves; those who have sufficient financial resources may hire labor to do this. All suranga are privately owned and, in the majority of cases, used individually by small family units. There are just a few instances where water rights are shared between families, usually in a usury or usufructuary arrangement, with water harvested in a rotation that is proportional to the land farmed by each tenant. Several suranga were shared by more than 1 family, even though suranga ownership always lies with 1 family. This scenario may happen through subdivision of a joint family or the division and sale of property and suranga that once belonged to a single owner.

FIGURE 2

Hydrogeology of suranga.

Water sources

On average, 35% of the irrigated area is covered by micro-irrigation systems in Karnataka (Aayog 2018). Water harvesting accounted for ∼47% of the irrigated area in Kasarogod in 2007 (Balakrishnan and Saritha 2007). Most of the farmers (65%) in this survey adopted a multiple source strategy of water harvesting using a combination of traditional techniques for their water supplies, including dug wells and occasionally river sources. In terms of combinations, the MCA indicated that only 8.5% of farmers were dependent on both bore wells and suranga. In contrast, most suranga were found in conjunction with dug wells, which suggests that demand is linked spatially to marginality. Sole reliance on suranga in a farm unit was rare, but where this happened multiple suranga were typically used.

Groundwater dating results gave a better understanding of the provenance of the possible water sources for suranga. Table 1 presents the equivalent “apparent” radiocarbon age to the reported pMC/fMDN value dates derived from suranga water sources as analyzed by Beta Analytic on 6 November 2013 and 2 November 2014. Based on these results, both suranga in Manilla village that were analyzed are most likely to be extracting water from a suspended phreatic aquifer found within the laterites. Gumpe suranga, which is part of a natural cave system and an open well on the other side of the hill from Manila village, has a rapid hydrogeological system that is more vulnerable to changes in weather patterns because of the rapid recharge rates in this system. Bore wells are clearly taking water from deeper semi- or totally confined aquifers.

TABLE 1

Provenance of groundwater sources using radiocarbon dates from different locations in Manila village collected in 2013/2014.

Water availability: Discharges from suranga in this survey ranged from 0.005 m³/s in the dry season to 0.1 m³/s in the wet season (Figure 3). In contrast Balooni et al (2010) calculated a larger range of discharges from 0.003 m³/s to 11.6 m³/s. Thus, groundwater availability varies significantly by season. No irrigation is required between the onset of the monsoon (late May) and late November because of an excess of water. Overexploitation of water is avoided as farmers show compunction on use during the dry season as less water flows out of the suranga. In the groundwater recharge catchment area for a suranga, afforestation, rainwater conservation, and groundwater recharge trenches or pits at the upper levels of hills can increase water availability inside a suranga (Malhotra et al 2007). Local government has funded these groundwater recharge initiatives (Shree Padre, water journalist, oral communication, 2014; Kelkar-Khambete 2012), not least because two-thirds of the rural population Karnataka still have no full access to water (Aayog 2018).

FIGURE 3

Typical discharges from 5 suranga.

Conveyance and storage: Suranga are used for both drinking water and irrigation. Farmers typically create a small earthen dam a few meters into the adit/tunnel to create a small pool of water. They then run a pipe of 2.5–5 cm in diameter, usually plastic or PVC, through the dam to collect a low but constant flow of water. This practice has the benefit of reducing the chances of contamination from around the entrance to the suranga, where it is most disturbed by mammals and reptiles. This becomes particularly important when the end use is drinking water, as bacterial infections, such as Escherichia coli, clearly need to be avoided. As far as irrigation is concerned, farmers typically adopt and integrate new irrigation technology, where appropriate, to improve the distribution efficiency of water (Crook et al 2016). This could include using drip irrigation, sprinkler systems, and hybrid micro-irrigation techniques, such as dripper, fogger, and bubbler systems. The natural pressure gradients created by steeply sloped fields facilitate the use of small spray irrigation networks or foggers. These devices can typically provide water at a rate of >10–12 L/h (Govind Bhat, suranga expert, oral communication, 2015). Drip-irrigation pipes are also used in conjunction with microcatchment techniques. At the opposite end of the spectrum, depending on the water availability, large hoses are sometimes used for short periods to irrigate tree crops. These are used in conjunction with small ponds and storage tanks that are found on most farms located on different terraces in the farm unit (Figure 4). Typically, storage ponds are built from earth and range in size but could store up to 21,600 L of water. From these, water is transferred under gravity either via open channels, but more typically via a small rubber or plastic pipe down the slope, with a maximum discharge rate (during monsoon) of 900 L/h and a minimum discharge rate (during summer) of 90 L/h.

FIGURE 4

Storage ponds typically associated with suranga.

Discussion

The design principles of suranga are unique, but the technology fits within a long history of water control on the Indian subcontinent (Agarwal and Narain 2005). Regionally, water-harvesting systems in Dakshin Kannada and Kasaragod have been well documented (Kokkal 2002; Balakrishnan and Saritha 2007; Halemane 2007; Balooni et al 2008, 2010; Kokkal and Aswathy 2009; Suseelan 2009), and several traditional vernacular systems of capturing water have been identified in the foothills of the Western Ghats. Hill suranga are used alongside other techniques of water harvesting found throughout India, such as wells, and storage techniques, such as small farm ponds; however, the hill topography negates the use of large tank systems (Shah 2003; Voudouris et al 2019). Only at the margins of the inhabitable area, usually near the tops of hills, where the poorest and most vulnerable farmers are concentrated, was there a greater dependency on suranga water because it is the only water supply. Suranga are dug only in these marginal zones. The government could promote suranga as an alternative to bore wells and to promote diversity in the use of different water resources as provenanced by the radiocarbon dates, but they have not done this, despite the pressures of increasing water scarcity under climate change (IPCC 2014; Fukushima et al 2019). To date, the provincial water authorities of Kerala and Karnataka typically only offer supportive funding for more efficient distribution techniques, such as drip irrigation. One farmer in Karnataka has accessed funds for labor costs to build a suranga from the Mahatma Gandhi National Rural Employment Guarantee Act, 2005, but this is atypical, and government authorities tend to overlook the system. The farmers, almost universally, were highly suspicious of government support and were content to remain autonomous and unregulated by government. Because conflict is so rare under private ownership of suranga, it is unsurprising that there are no formal conflict resolution systems in place. The same is not true for bore well use, which can lead to over-abstraction. Both the provincial and national government have been very slow to regulate bore well use through any centralized licensing scheme and have ignored their unregulated impact on the water supplies of traditional techniques like suranga. The National Green Tribunal (NGT) has not yet adjudicated on any environmental issues related to suranga, but recent NGT judgements such as Original Application No. 176/2015 from North India, recommending the protection, conservation, and augmentation of traditional water-retaining structures, could point to the possibility of future NGT interventions on over-abstraction from bore wells. To date, the promotion of the sustainable properties of suranga technology have been championed only by local water journalists who report through the Indian Water Portal (including our work), and small nongovernmental organization (NGO) research units, like the Varanashi Research Centre, which operates in the foothills of the Western Ghats. Some large-scale national NGOs, like the Development of Humane Action, have started to show interest in the sustainable credentials of suranga, and these may prove to be a more efficient conduit for getting information to the central government. The identification of perched aquifers as the predominant water source for suranga could point to this relatively new technology being resilient to the pressures of an unregulated expansion of bore wells that threaten the carrying capacity of groundwater supplies only when there is overlap of different water-harvesting techniques, which is rare. Thus, it becomes prudent to examine how the suranga system sits in relation to similar traditional and older groundwater-harvesting techniques as a sustainable technology.

Many authors have compared the design principles of suranga with ancient qanat technology. The scale of suranga better fits what Ward-English (1968) referred to as those smaller qanats found in mountainous areas that are usually short, shallow tunnels only tens of meters long and several meters deep, which draw surface water from small patches of alluvium. Work in Israel also points to smaller-scale spring systems known as niqba' (Ron 1985; Yechezkel and Frumkin 2016) being similar in design and scale to suranga (Yechezkel, oral communication, 2019). Some early Hellenic aqueducts in places like Polyrrhenia are also of a similar design and scale as suranga (Voudouris et al 2013). Both these cases are spring-fed systems in karstic environments. The geomorphological determinant of suranga is very different with all systems exclusively tunneled in laterites. Many systems appear from the carbon dating to be supplied from perched aquifers, which is unique for a groundwater-fed irrigation system. The starting point for suranga building, like that for niqba', is typically from the entrance and not from a mother well. There is no evidence of aboveground leveling and the use of refraction techniques that were typically used during qanat construction (Stiros 2006) and, therefore, the internal construction techniques in suranga are different. A technique of constructing hybrid wells in deep wells in the Middle East to increase the capacity of the well (Helweg 1973) is similar to enhancing water supplies in dug- and stepped-well suranga. Qanat draw water from mountainous areas and transfer this to lowlands and plains, whereas the suranga system is found exclusively in hilly areas. Suranga take from a couple of months to a year to construct, which is in marked contrast to larger-scale qanat that can typically take 20–30 years to construct (Esfandiari 2007). The levels of maintenance of qanat and suranga are diametrically opposite in scale, commitment, and cost (Esfandiari 2007). At no stage has a suranga become a hazard to other people, unlike some qanat that pass under built environments (Abbasnejad 2017). Suranga have branches (kai) at the proximal end of the structure, which is near the water source; in contrast, qanat will usually branch only at the distal end of the system to aid distribution of the water (see Remini 2018). Thus there are morphological differences between the two tunneling systems. Likewise, the shape of the tunnel or gallery can be much more variable for a qanat (see Remini 2016: 52) than it is for a suranga, which is molded to the shape of the main digger. The etymology of qanat system structures and practices found as far west as the Maghreb and the Canary Islands (Lightfoot 2000; Esfandiari 2007; Boualem et al 2014; Dahmen and Kassab 2017) and as far east as China (Mächtle et al 2009) and possibly Japan (Takamura 2018) share similarities, but the language of suranga is nontechnical. Overall, qanat are a good example of a successful transferable technology; the question remains whether suranga could be the same. Suranga technology has spread through word of mouth to other parts of India, where similar laterites and hydrological conditions have been found. There is nothing in principle stopping suranga from being transferred to other hilly regions of the world with similar types of laterite, topography, and hydrological regimes. A preliminary search has identified Ethiopia as a possible hilly country with laterites that may have the potential for transfer where a water resource need can be identified.

Conclusion

Overall, the use of suranga in a multisource strategy is a sensible risk aversion strategy under conditions of climate change, as by drawing on different sources of groundwater farmers minimize the risk of running out of water during the dry season. There are signs of an adaptive response among most farmers to water scarcity, regardless of their level of security of tenure, caste, or level of poverty, and of adopting new conveyance and distribution techniques in conjunction with traditional postmonsoon storage of water in farm ponds for irrigation. By prioritizing some suranga systems for drinking and others for irrigation, farmers from all backgrounds can mitigate these problems. In terms of existing extension services, the Kerala State Ground Water Department (KSGWD) provides technical expertise to local government agencies, quasi-government agencies, farmers, and individuals, and it identifies sites for tube wells, bore wells, filter-point wells, hand-pump wells, open wells, and other types of wells, but not suranga (Balakrishnan and Saritha 2007). Heavy subsidies are also provided by the KSGWD to marginal and poor farmers for survey, drilling, and electricity charges for pump sets that remain fixed at a low rate despite the rate of use (Balooni et al 2010). This imbalance in local government/water authority support is not generally viewed as a problem for farmers, even those below the poverty line, as they can build their own suranga at a lower cost than other groundwater abstraction techniques. Thus, there is a pressing need for better understanding of perched aquifer water supplies that mainly supply suranga, as they provide an alternative to scarce water supplies in deeper, more slowly recharging, or confined aquifers supplying most bore wells, and thus they potentially offer a more sustainable use of water. There is a clear need for more government intervention toward regulating bore well digging and groundwater abstraction. Where there is potential for both bore wells and suranga, farmers are opting for the former and so shaping a future where suranga become less valued, even though the technology is comparatively more sustainable. Finally, it is argued that minimal external intervention in suranga construction should occur, as the antecedents for their historic success lie in individual self-determination. This work therefore warns against ubiquitously applying communal responses to water resource management in mountain environments as best practice.