To obtain an understanding of how farmers view their water resources, we asked village leader respondents to describe the nature of the aquifers that are under their villages. Because most village leaders have not been a part of any hydrogeological surveys, they often were not able to answer questions concerning the existence, size or other geological properties of the aquifers. Instead, village leaders knew more precisely how many shallow and deep wells there were in their village as well as the depths of those wells. Although there is no complete correlation between the depth of the wells and the nature of the aquifer, in many cases, the existence of shallow or deep wells coincides with that of shallow or deep layers of village aquifers. Regardless of their exact hydrogeological properties, according to our data (and the perception of village leaders), 'deep wells' are almost always having a depth of at least 60 m. If a village needs to drill through an aquitard (a clay layer in most cases) to sink a well, the well is always defined as a 'deep well'. Shallow wells, in contrast, are mostly less than 60 m and do not penetrate an aquitard.
Whether deep or shallow, groundwater resources are extensive across regions of northern China. We asked village leaders if there were groundwater resources in the village. Most replied that there were, and the share of villages having these was almost 95% in 2004. However, not all villages having groundwater use this resource for irrigation. In 2004, more than 15% of irrigated villages with groundwater did not use it for irrigation. We further explore the reason behind this. According to the village leader respondents, there were two major reasons for not using it. Research results show that in 2004, the most important reason was that there were cheap and sufficient surface water resources (51% of villages). The second important reason was that there was no money to dig tube wells (37% of villages). Such findings suggest that there still may be potential to use greater volumes of groundwater resources in the future. With increasing water scarcity and rising water demands, more villages have begun to use their community's groundwater. For example, from 1995 to 2004, the share of villages using groundwater resources for the first time had increased by almost 12%.
Relying on the observations of our NCWRS respondents, one of our most prominent findings was the great diversity of aquifer development in northern China. Of the 238 sample villages that used groundwater for irrigation in 2004, 33% told us that they extracted groundwater only from shallow aquifers, 42% only from deep aquifers and the remaining 25% from both. Our data show that in some villages in northern China, the groundwater supply from shallow aquifers is sufficient to support current local water demand for irrigation. In other villages, maybe due to exhausted or unusable shallow aquifers, farmers extract groundwater only from deep aquifers.6 In some villages (25%), both shallow and deep aquifers are being used. The groundwater supply from shallow unconfined aquifers is highly dependent upon precipitation, which supplies groundwater recharge. When rainfall is above average, as it was in 2004, water levels increase in shallow aquifers due to above-average recharge. This may be the reason that more villages extracted groundwater from shallow aquifers in 2004 than in 1995.7
According to our respondents, the depth to water also varied across northern China. Although the average depth to water in 2004 was 26 m, it varied sharply across our sample villages (Fig. 3.3). In fact, in most villages depth to water was fairly shallow. In 2004, the average depth to water for the villages from the shallowest quartile of villages was only 4 m and that for the second quartile was only 9 m. Villages in the third quartile were pumping from an average depth to water of more than 30 m. In only 4% of groundwater villages were villagers pumping from more than 100 m.
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