Proximate and underlying drivers of socio-hydrologic change in the upper Arkavathy watershed, India

Abstract

Abstract. Addressing water security in the developing world involves predicting water availability under unprecedented rates of population and economic growth. Yet the combination of rapid change, inadequate data and human modifications to watersheds poses a challenge, as researchers face a poorly constrained water resources prediction problem. This case study of the data-scarce, upper Arkavathy watershed, near the city of Bengaluru in southern India, attempts to systematically 5 explain the observed disappearance of surface and groundwater in recent decades. The study asks three questions: 1) Can we quantify the change attributable to different drivers? 2) Can we anticipate change? 3) What policy lessons can be drawn? Field experiments, isotopic studies, borewell scans and sensors were deployed to understand hydrologic processes over five years. These were used in a historical reconstruction of the catchment over three decades that replicates the decline. The multi-10 scale model of the upper Arkavathy, quantifies the contributions of soil and water conservation measures, groundwater depletion and eucalyptus plantations to the decline in surface and groundwater resources. The model results indicate that the catchment hydrology cannot be reconstructed without explicitly including human feedbacks. The system is influenced by both endogenous drivers (social feedbacks to changes in water availability such as irrigation efficiency improvements, soil and 15 water conservation measures and deeper borewells) and exogenous drivers (technological change, pro-development governance and economic forces due to urbanization, which provided access to capital and markets for high-value crops). The research suggests that in a system where productivity of the landscape is limited by water, economic drivers will always push for maximization of water abstraction and use. Unsustainability of resource use is inevitable, in the absence of credible controls 20 on abstraction and use, 1 Hydrol. Earth Syst. Sci. Discuss., https://doi

The Groundwater Recovery Paradox in South India

“…In contrast, their survey of wells in the region found no visible open wells with water. A more focused analysis based on a detailed survey 472 borewells in a small (26 km 2 ) subcatchment of the Arkavathy watershed revealed that the median depth of the borewells farmers were digging increased from <50 m in 1970s to over 200 m in 2000s (Srinivasan et al, ). Deeper borewells are a clear indication of disappearing groundwater, despite CGWB wells recording no significant trends in this region.…”

Digging deep and running dry—the adoption of borewell technology in the face of climate change and urbanization

“…These tanks were used and managed at the communal level. Since the 1990s, however, many farmers have decided to exit the communal irrigation system by investing in private well equipment to extract groundwater (Srinivasan et al, 2017). The reasons for this are manifold.…”

“…Third, pumping technology and drilling have become cheaper in absolute and relative terms. Domestic production of pumps and improved drilling technologies have lowered the cost of establishing a borewell, and input prices have decreased through subsidized flat rate electricity prices (Srinivasan et al, 2017). Moreover, increased output prices for agricultural products have also contributed to lowering the relative price of groundwater irrigation (Kajisa et al, 2007).…”

“…Though agricultural intensification can considerably improve smallholders' livelihood, increased uptake of borewell technology comes at a cost. More wells and uncontrolled water extraction have already led to overexploited aquifers in several regions of India, particularly in the western and southern states including the Bangalore area (Blakeslee, Fishman, & Srinivasan, 2020;Srinivasan, Penny, Lele, Thomas, & Thompson, 2017). As a consequence, borewells dry up, threatening the well-being of water users.…”

“…Thus, adoption decisions in this part of the world focus more on the access to groundwater itself than on technologies for efficient water use. To enhance agricultural productivity the Indian government subsidizes borewell implementation and electricity for pumping water despite concerns of overexploited aquifers; water extraction is hardly regulated and generally free of cost once a borewell is installed (Srinivasan et al, 2017). This is in clear contrast to the water management policies in the Global North, where groundwater access is strictly regulated and studies show that water prices, for example, have a statistically significant effect on adoption decisions (Alcon et al, 2011;Caswell & Zilberman, 1985).…”