Mahesh R. Gautam

Climate change in arid lands and Native American socioeconomic vulnerability: The case of the Pyramid Lake Paiute Tribe

The case of the Pyramid Lake Paiute Tribe exemplifies tribal vulnerabilities as a result of climate change. Preliminary socio-economic data and analysis reveal that the tribe’s vulnerability to climate change is related to cultural and economic dependence on Pyramid Lake, while external socio-economic vulnerability factors influence adaptive capacity and amplify potential impacts. Reduced water supplies as a consequence of climate change would result in a compounded reduction of inflows to Pyramid Lake, thus potentially impacting the spawning and sustenance of a cultural livelihood, the endangered cui-ui fish (Chasmistes cujus). Meanwhile, limited economic opportunities and dwindling federal support constrain tribal adaptive capacity. Factors that contribute to tribal adaptive capacity include: sustainability-based values, technical capacity for natural resource management, proactive initiatives for the control of invasive-species, strong external scientific networks, and remarkable tribal awareness of climate change.

Climate Change in the Himalayas: Current State of Knowledge

This paper reviews the literature on the potential biophysical and economic impacts of climate change in the Himalayas. Existing observations indicate that the temperature is rising at a higher rate in Nepal and Chinese regions of the Himalayas compared with rest of the Himalayas. A declining trend of monsoon in the western Indian Himalayas and an increasing trend in the eastern Indian Himalayas have been observed, whereas increasing precipitation and stream flow in many parts of Tibetan Plateau are noted. Glaciers in both the eastern and western Himalayas are mostly retreating, but the majority of the glaciers in Karakorum are either stable or advancing slowly. Expansion of glacier lakes is reported, with the highest rate in Nepal and Bhutan. Most literature predicts increases in temperature and monsoon precipitations and decreases in winter precipitations in the future thereby leading to monsoon flooding and increased sediments in stream flow. Available hydrological simulations indicate reduced rainfall and shrinkage of glacier thereby leading to shortage of water supply for power generation and irrigation in winter particularly in highly glaciated basins. Projected economic impacts of glacial lake outburst floods can be substantial on the developed river basin with infrastructures and population centers. However, there is a clear gap in knowledge of economic impacts of climate change in the Himalayas.

Streamflow trends in Nepal

Abstract This study presents the first comprehensive nationwide trend detection of streamflow in Nepal, a country that has been historically understudied despite its critical location as the southern pathway for most of the Himalayan snowpack melt and torrential seasonal monsoon rains. We applied Mann-Kendall and Sens trend tests using trend-free pre-whitening and bootstrap approaches to two streamflow data sets to deal with serial and cross-correlation. The two data sets comprised 23–33 hydrometric stations with 31 years and more than 20 years of published data, respectively. The test on the 33 stations data set showed that 23% of the streamflow variables studied had statistically significant trends, evenly divided between upward and downward trends. Similarly, in the second, relatively smaller data set, 24% of variables exhibited trends, of which 41% were downward and 59% upward. The higher percentage of observed upward trends in pre-monsoon and winter seasonal average flow is noteworthy given the potential snowmelt contribution in many of the studied sites. Trends were mostly absent in stations draining the larger basins. However, some spatial patterns were seen in the observed trend directions, specifically, a downward trend in the Karnali-Mahakali River basin and an upward trend in the West Rapti River basin, as well as a nationwide absence of trend in the post-monsoon season. Editor Z.W. Kundzewicz Citation Gautam, M.R. and Acharya, K., 2011. Streamflow trends in Nepal. Hydrological Sciences Journal, 57 (2), 344–357.

Bacterial contamination due to point and nonpoint source pollution in a rapidly growing urban center in an arid region

The distribution of bacterial contaminants (Escherichia coli and total coliforms) and nutrients (nitrogen and phosphorus) in a rapidly growing metropolitan area, the Las Vegas Valley, were studied to assess the contributions of point and nonpoint pollution sources under dry weather flow (pre rainfall) and wet weather flow (post rainfall) events. Nonpoint sources emanating from urban centers and septic seepage were found to be a primary source of bacterial contamination in the Las Vegas Wash, a mainstream wash channel where the Las Vegas Valley watershed drains. Contribution of point sources (wastewater treatment plants) to E. coli and total coliforms were found to be negligible. However, data in the Tropicana/Flamingo Wash, a tributary of the Las Vegas Wash, showed high bacterial activities in the wet antecedent rainfall condition as compared to the pre-rain dry antecedent condition suggesting that the rainfall increased bacterial activities.

Unique Challenges Facing Southwestern Tribes

The Southwestern United States is home to 182 federally recognized tribes (Federal Register 2010, Figure 17.1). California has the largest number of tribes (109), and the largest Native American population in the country (Table 17.1). Arizona, New Mexico, Colorado, and Utah are also home to seven of the most populous tribes, with populations ranging from 10,000 to over 300,000 (U.S. Census 2010). Nine tribes in the Southwest are considered “large land-holding tribes,” five of which are among the ten largest reservations in the United States, ranging in size from 600,000 to 15 million acres (Federal Register 2010). More than one-third of the land in Arizona is tribal land.

Evaluation of bendway weir bank stabilization techniques for stream restoration

In this study, velocity distribution patterns in a stream in the presence of bendway weirs were assessed for their effectiveness in bank stabilization in a demonstration site in the Las Vegas Wash, Nevada, USA. Streambanks of the target stream had been stabilized previously by longitudinal stone toe protection (LSTP) and stone spur dikes. Stone toes are meant to protect the toe of streambanks. Similarly, stone spur dikes consist of a series of dikes (of a crest relatively higher than that of the bendway weirs) protruding at right angles from the convex side of the streambanks. Velocity measurements were taken to evaluate the velocity field in the channel in the following three different cases: Case 1, channel with LSTP and the pre-existing spur dikes; Case 2, channel with LSTP with no deflecting structures (spur dikes removed); and Case 3, channel with LSTP and bendway weirs. The results suggested that bendway weirs caused a reduction in the uncontrolled high-velocity flow near the outer bank (right bank), allowing only controlled flow. Thus, bendway weirs were found to be more effective than spur dikes in reducing the velocity of flow at the vulnerable weir zones near the outer banks, thus providing a means to stabilize the streambanks.