3.1. Hydrologic Setting
Peak flow in the Upper Naryn occurs in late July or early August, while the Lower Naryn experiences an earlier peak in late May or early June. The Naryn River hydrograph shape across elevations demonstrates the transition from ice to snow melt sourced waters as the river progresses downstream. The upper gauge (Chong Naryn) exhibits a typical sustained late summer flow shape of a glacier sourced system, while the lower elevation gauge at Uch Terek shows more water mass and higher flows earlier in the year coincident with the spring snow melt season (Figure 2
). The “flashy” character of the annual hydrograph’s rising limb suggests a river system that is fairly responsive to the highly variable precipitation inputs over the course of the year (Figure 2
Rain during the drier months almost always comes in multi-day storms, and in the rainy months the intensity can vary by an order of magnitude from day to day. Based on the 14 years of MERRA precipitation data across nine 500 m elevation bands (500 m to 4500 m), 70% of the months record both rain and snow event within the same elevation band. This suggests rain-on-snow events may exacerbate the high magnitude response of stream flow to new precipitation inputs across elevations. Since glaciers play a role reducing both intra- and inter-annual flow variability by providing a consistent ice melt supplied baseflow through the melt (summer) season that is independent from storm spikes, depletion of ice mass in glacier systems will lessen the water they supply to river systems over the long term and may impose a hydrograph that is even more responsive to changes in weather.
A substantial baseflow of approximately 200 m3 s−1 is observed outside of the melt season at the regional basin scale shown at the Uch Terek gauge, while consistent but smaller baseflows are present in the Upper Naryn. A small run-of-river reservoir is located immediately upstream of Uch Terek flow gauge and may account for the highly consistent winter flow recorded at this point.
Precipitation across the basin averages 27.13 cm per year, with 63% falling as rain and 27% falling as snow, however above 3000 m the total precipitation inputs are approximately half rain and half snow. In relation to the way the basin is split in this paper for analysis, approximately 40% of precipitation in the Upper Naryn falls as snow. Within the Lower Naryn Basin, annual precipitation inputs are comprised on average of 89% rain.
In the Upper Naryn basin, 84% of the area (8632 km2
) has snow probability >30% while this figure applies to 54% (20,424 km2
) of the Lower Naryn basin area (Figure 3
). Glaciers are present at the headwaters and provide melt inputs to both headwater stems as well as to the Ak-Tal, a major tributary joining the Naryn River at Dostuk. Glacier ice covers 994 km2
, or 2% of the entire study domain.
3.2. Hydro Chemistry Elevation Gradient
Isotope variation of Naryn River waters across the elevation gradient show a strikingly consistent isotope value throughout the basin (Figure 4
O values for mainstem waters hover around −12‰ from the highest elevation sample all the way through to Toktogul Reservoir. Tributary sample δ18
O values vary more than the mainstem ranging from −13‰ to −9‰. Notably, crysopheric end member samples—Snow, ice, glacial outflow and high elevation groundwater—bracket the isotope values found in the Naryn River. In contrast, the rain sample acquired in the adjacent Kyzyl Suu basin has a δ18
O value of 0‰, suggesting that surface waters in the Naryn basin are dominated by melt water sources. With the exception of the groundwater spring at Kazarman Pass (2299 m, −16‰), groundwater isotopes throughout the basin (−13‰ to −11‰) also hover near the isotopic values of the high elevation melt water group and are discretely different than rain.
The ion concentration progression demonstrates the combined influence of groundwater contributions and mine discharge on the chemical signature of mainstem waters (Figure 4
b,c). The mine discharge sample provides exceptionally high levels of SO42−
(25,387 μeq L−1
) and Na+
(24,596 μeq L−1
) to the mainstem waters. However, it is Ca2+
poor (599 μeq L−1
) and does not account for the high Ca2+
values observed in both mainstem waters and tributaries that are hydrologically disconnected from the mine discharge waters (e.g., Bordu Stream and Arabel River). Extremely elevated levels of Ca2+
(4116 μeq/L, twice the level of Ca2+
in the mainstem) were found in the Bordu alpine groundwater sample that logically also contributes to high elevation river flow. These groundwaters are SO42−
poor (453 μeq L−1
and 238 μeq L−1
, respectively), and so there is intuitively a joint contribution from mine discharge waters and groundwater that accounts for the elevated ion profile of the Kumtor (Upper Naryn) River.
Dilution of ions with decreasing elevation likely result from added ion-poor snowmelt contributions as the catchment expands to include major additional sub-basins adding significant alpine areas and snow cover to the basin. This dilution trend is observed until 3182 m in the Ca2+
profile (Figure 4
b), then reverses towards an increasing concentration pattern likely a result of groundwater contributing increasing proportions to the river flow.
3.4. Socio-Hydro Results
Survey results indicate a common response across all communities relating to an overall decrease in water access over the last 15 years. Survey participants stated that water availability depends not on the physical water supplies but primarily on water management and infrastructure investment for both municipal and irrigation systems. Much of the water stress stems from agricultural reorganization after the Soviet collapse from large collective farm structures to individual, small private farms. This transition lies at the root of many factors contributing to current water stress across Naryn River basin communities. The deputy water manager in Naryn province summarized several factors, including:
Gaps in knowledge. Farmers accustomed to single task jobs associated with large scale farming practices lacked knowledge about crop rotation, irrigation techniques suitable for the climate and soils of the Naryn basin, and the complete cycle of agricultural production needed for productive small-plot farming.
A lack of agricultural, economic, educational and hydrologic infrastructure needed to service small-plot farmers. Farmers were ill-equipped without financing options, reliable irrigation and water distribution, and appropriate machinery. As a result, yields declined and irrigation systems deteriorated leading to greater inefficiencies.
Complete absence of new irrigation technologies.
Inadequate government support for struggling farmers due to understaffed water management offices in the region. A shortage of qualified specialists was largely attributed to low compensation.
The impacts to the agricultural sector due to the transition between large-to-small scale farming demonstrates a shift in water-human experiences from one that was nationally regulated to one where communities are largely responsible for addressing water needs. Some communities responded to water supply stress by installing groundwater wells, especially for drinking water. The survey results show that changes to water supply sources (surface water versus groundwater well) are not dependent on water availability or location within the basin. For example 2 out of 6 surveyed communities with heavier reliance on groundwater are unregulated upstream communities, Naryn and Kazarman, communities one may expect to be more heavily tied to the surface flows of the Naryn River. Water quality—not quantity—motivated the increase in groundwater use.
In contrast to these two communities’ adaptive responses, the regulated downstream communities near Toktogul preferred tributary surface water sources and traditional Soviet community based water systems such as gravity fed canals and water storage. Despite these preferences, upon relocation reservoir communities were provided with electric pumps to extract lower-lying water to service the village. These pumps were a common gripe among survey respondents, as they require continual maintenance and are notoriously prone to failure, decreasing overall reliable access to water.
A comparison of survey results shows that source of income was one of the most obvious differences over time in unregulated upstream versus regulated downstream communities. Income shifted from salaries paid by state run organizations in 2000 to small businesses, water-efficient crops and livestock in unregulated upstream communities while in regulated downstream communities income increasingly comes from labor migration and associated remittances. Downstream survey participants indicated that factors contributing to this difference include smaller land plots per household and less water supplies in regulated downstream communities, which are not enough to provide food for households.
Apart from these changes, it was obvious that even though the price of water increases in downstream communities, at some point the price of water does not really matter in light of much bigger issues faced by regulated river basin communities near Toktogul reservoir. The biggest issues in the Toktogul district are limited water availability, land and funds scarcity, and lack of trust in government, all of which were being perceived by the local communities as a direct result of communities’ relocation and hydropower development in the region in 1960s. As a result, survey respondents in regulated river basin communities indicated that there were no positive socio-economic changes within their communities in the last 15 years.
This observation is strikingly different from the survey replies in the upstream communities where survey respondents were much more optimistic in their ability to change things, turn things around, or earn enough income with existing resources. One survey response summarizes the general attitude in the upstream communities: “If there will be another dry season (no rain and less water flow in the river), we will farm a different crop, like wheat, that requires less water.” Indeed, respondents in all communities noted that the majority of farmers shifted agricultural production from water-intensive crops grown under Soviet rule (e.g., vegetables and fruits), to less water-intensive crops such as alfalfa and barley to feed livestock.
Survey respondents in all communities brought up the topic of climate change, albeit with different emphasis. Upstream communities are aware that warmer temperatures may threaten their normal agricultural production cycle, including an observed shift in peak flows that they attribute to climate changes now misaligns water arrival with the height of the growing season. The survey respondents in regulated downstream communities acknowledged climate change but it was a lesser focus as compared to their counterparts in upstream communities.
In summary the survey found that Naryn basin communities responded to changes in water supplies, water flow, hydropower and irrigation projects at various levels. The responses suggest that the overall impact in communities is a mixture of actions on mainly household, farm, private firm and organization levels. These actions include a heavier reliance of some municipalities on groundwater, shifting to less water-intensive crops and/or livestock, and transitioning from agricultural sources of income to labor migration and associated remittances.