A study on drought and wet conditions in different ٢ basins and climates ٣

Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran ٧ vali-pour@hotmail.com ٨ Abstract: The Surface Water Supply Index ( ٩ conditions and agricultural water management. By using this indicator, ١٠ of Colorado and Oregon basins were investigated ١١ values can also be plotted as a time series graph while critical years were specified. This allows the ١٢ user to graphically visualize the values from year to year and ١٣ change from year to year. Managers can then refer to records from critical years in determining ١٤ strategies for dealing with the current years’ water supply. Also evident is whether the ١٥ component or the reservoir component is the predominant driving force at any given time. SWSI's ١٦ can be an excellent water management tool in determining overall risk and management strategies. ١٧ It gives the water user and manager more information ١٨ alone. According to the results, obtained categories based of SWSI values are indicated hydrologic ١٩ conditions for Colorado and Oregon States with two different climates. Although decisions only ٢٠ based on geographic and climatic information due to the insufficient and sometimes contradictory ٢١ results than the SWSI can cause water loss or increase the risk of drought. ٢٢


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Abstract: The Surface Water Supply Index ( ٩ conditions and agricultural water management. By using this indicator, ١٠ of Colorado and Oregon basins were investigated ١١ values can also be plotted as a time series graph while critical years were specified. This allows the ١٢ user to graphically visualize the values from year to year and ١٣ change from year to year. Managers can then refer to records from critical years in determining ١٤ strategies for dealing with the current years' water supply. Also evident is whether the ١٥ component or the reservoir component is the predominant driving force at any given time. SWSI's ١٦ can be an excellent water management tool in determining overall risk and management strategies.

١٧
It gives the water user and manager more information ١٨ alone. According to the results, obtained categories based of SWSI values are indicated hydrologic ١٩ conditions for Colorado and Oregon States with two different climates. Although decisions only ٢٠ based on geographic and climatic information due to the insufficient and sometimes contradictory ٢١ results than the SWSI can cause water loss or increase the risk of drought. ٢٢ ٢٣ Keywords: Colorado; Oregon; water ٢٤ PACS: J0101 ٢٥ ٢٦

Introduction ٢٧
Scrutiny of hydrologic parameters espe ٢٨ estimating of flood and drought periods for prevent of their damages has always been concern of ٢٩ hydrologists. Garen [1] revised SWSI for Western United States. He suggested that indexes for ٣٠ individual hydrologic components be developed to provide supporting information to the SWSI.

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Shafer and Dezman [3] developed SWSI to assess the severity of drought conditions in snowpack ٣٢ runoff areas. Hoekema and Sridhar [2] using surface water supply and soil moisture indic ٣٣ climatic attributes and water resources allocation in the Snake River basin, Idaho. The results ٣٤ indicates that the decline in midseason and late season diversions is mostly caused by decreasing ٣٥ supply in the study period, while a comparison of d ٣٦ precipitation index indicates that early season diversions are highly correlated to early season ٣٧ moisture anomalies. Unfortunately, much research has not been done on SWSI and role of surface ٣٨ water supply index has not been considered in other studies about water resources management ٣٩ [ [4][5][6][7][8][9][10][11][12][13][14][15][16]. Therefore, necessity of this study is specified. ٤٠

Materials and Methods ٤١
The surface water supply index (SWSI) is a predictive indicator of total surface water ٤٢ availability within a watershed for the spring and summer water use seasons as follows: ٤٣ Surface Water Supply Index (SWSI) may be considered for studying conditions and agricultural water management. By using this indicator, water resources conditions Colorado and Oregon basins were investigated from extremely wet to extreme drought. The SWSI values can also be plotted as a time series graph while critical years were specified. This allows the the values from year to year and to see how the current year's values change from year to year. Managers can then refer to records from critical years in determining strategies for dealing with the current years' water supply. Also evident is whether the component or the reservoir component is the predominant driving force at any given time. SWSI's can be an excellent water management tool in determining overall risk and management strategies. It gives the water user and manager more information than simply streamflow or reservoir level , obtained categories based of SWSI values are indicated hydrologic conditions for Colorado and Oregon States with two different climates. Although decisions only and climatic information due to the insufficient and sometimes contradictory results than the SWSI can cause water loss or increase the risk of drought.
water Scrutiny of hydrologic parameters especially SWSI for water resources management and estimating of flood and drought periods for prevent of their damages has always been concern of hydrologists. Garen [1] revised SWSI for Western United States. He suggested that indexes for ic components be developed to provide supporting information to the SWSI. Shafer and Dezman [3] developed SWSI to assess the severity of drought conditions in snowpack runoff areas. Hoekema and Sridhar [2] using surface water supply and soil moisture indic climatic attributes and water resources allocation in the Snake River basin, Idaho. The results indicates that the decline in midseason and late season diversions is mostly caused by decreasing supply in the study period, while a comparison of diversions to Palmer index and the standardized precipitation index indicates that early season diversions are highly correlated to early season moisture anomalies. Unfortunately, much research has not been done on SWSI and role of surface x has not been considered in other studies about water resources management 16]. Therefore, necessity of this study is specified.
The surface water supply index (SWSI) is a predictive indicator of total surface water ty within a watershed for the spring and summer water use seasons as follows: may be considered for studying hydrologic water resources conditions from extremely wet to extreme drought. The SWSI values can also be plotted as a time series graph while critical years were specified. This allows the see how the current year's values change from year to year. Managers can then refer to records from critical years in determining strategies for dealing with the current years' water supply. Also evident is whether the streamflow component or the reservoir component is the predominant driving force at any given time. SWSI's can be an excellent water management tool in determining overall risk and management strategies. than simply streamflow or reservoir level , obtained categories based of SWSI values are indicated hydrologic conditions for Colorado and Oregon States with two different climates. Although decisions only and climatic information due to the insufficient and sometimes contradictory cially SWSI for water resources management and estimating of flood and drought periods for prevent of their damages has always been concern of hydrologists. Garen [1] revised SWSI for Western United States. He suggested that indexes for ic components be developed to provide supporting information to the SWSI. Shafer and Dezman [3] developed SWSI to assess the severity of drought conditions in snowpack runoff areas. Hoekema and Sridhar [2] using surface water supply and soil moisture indices related climatic attributes and water resources allocation in the Snake River basin, Idaho. The results indicates that the decline in midseason and late season diversions is mostly caused by decreasing iversions to Palmer index and the standardized precipitation index indicates that early season diversions are highly correlated to early season moisture anomalies. Unfortunately, much research has not been done on SWSI and role of surface x has not been considered in other studies about water resources management The surface water supply index (SWSI) is a predictive indicator of total surface water ty within a watershed for the spring and summer water use seasons as follows: Where a, b, c, and d are weights for each component and must meet the condition a+b+c+d=1.

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Each basin has a unique a, b, c, and. PN shows probability of non-exceedance (%) and snow, prec, ٤٦ strm, and resv refer to snowpack, precipitation, streamflow, and reservoir componens, respectively.

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The revised formulation of the SWSI as follows: Where fcst refer to streamflow forecast.

٥٠
SWSI values are scaled from +4.2 (abundant supply) to -4.2 (extremely dry) with a value of zero ٥١ (0) indicating media water supply as compared to historical analysis. SWSI used especially where ٥٢ palmer drought index does not adequately reflect conditions in snow-dominated regions.

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Colorado  Figure 1 shows Colorado and Oregon States with their basins. ٦٦

Results and Discussion ٦٧
In order to study the hydrologic condition of Colorado and Oregon basins, the SWSI values ٦٨ were divided into the 11 different categories (Table 1). The average SWSI values of Colorado states ٦٩ shows that this state is wet, of hydrologic conditions (only one basin has the SWSI less than zero).

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Unlike this state, the Oregon state hydrologic conditions can be evaluated as dry according to the ٧١ average SWSI values (only one basin has the SWSI more than zero). Due to the mild climate of ٧٢ Oregon, extremely wet and extreme drought hydrologic conditions not observed in any of this ٧٣ state's basins. Even percent of very wet and severe drought hydrologic conditions were very lower ٧٤ than other hydrologic conditions. But in Colorado state due to the continental climate role of very ٧٥ wet and severe drought categories were significant. To better assess of the hydrologic conditions can ٧٦ be used from Figures 2 and 3.

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In Gunnison basin, mild drought condition is dominant. In Colorado, Arkansas, San Juan, ٧٨ Animas, Dolores, and San Miguel basins hydrologic condition is near normal. Hydrologic condition ٧٩ in Yampa, White, and North Platte is moderate drought. This basin has the lowest average SWSI ٨٠ among Colorado basins (Table 1). Thus, Gunnison, Yampa, White, and North Platte basins due to ٨١ the more probability of drought exceedance should be in priority of water resource allocation, terms ٨٢ of the management. Finally, in South Platte and Rio Grande basins hydrologic condition is very wet ٨٣ and slightly wet, respectively. So, preventive measures are necessary to prevent flooding in South ٨٤ Platte basin. In particular, it has the largest catchment area among of Colorado basins along ٨٥ Arkansas basin (Figure 1). It is noteworthy amount of average SWSI in South Platte basin is ٨٦ maximum ( Table 1) whereas climate of the eastern Colorado (South Platte and Arkansas basins) is ٨٧ semi-arid with low humidity and moderate precipitation, usually from 380 to 630 mm annually.

٨٨
Therefore, the climate alone cannot reveal the hydrologic conditions. As geographic information ٨٩ alone is not a criterion for hydrologic judgment: areas.

٩٦
According to the Figure 3 in North Coast, South Coast, Willamette, Lower Deschutes, Umatilla, ٩٧ Upper John Day, Harney, Grande Ronde, Rogue, and Umpqua basins hydrologic condition is near ٩٨ normal. In Klamath, Lake, Owyhee, Malheur basins hydrologic condition is mild drought. These ٩٩ basins have the lowest average SWSI among Oregon basins (Table 1). Thus, these basins due to the ١٠٠ more probability of drought exceedance should be in priority of water resource allocation, terms of ١٠١ the management. Finally, in Upper Deschutes basin hydrologic condition is slightly wet. It is ١٠٢ noteworthy amount of average SWSI in this basin is maximum among Oregon basins (Table 1).

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The effect of geographic condition on climate is very more than hydrology in this state. The ١٠٤ mountains of the Cascade Range act as a divide between the western and eastern sides of the state.

١٠٥
The decisions only based on geographic and climatic information due to the insufficient and sometimes ١٢٣ contradictory results than the SWSI can cause water loss or increase the risk of drought. ١٢٤

Conflicts of Interest:
The authors declare no conflict of interest.

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.  calculated by dividing number of the SWSI in each category to all data ٢٠٨