Long‐term hydrologic simulation using SCS‐CN‐based improved soil moisture accounting procedure

Abstract

Abstract:The Soil Conservation Service Curve Number (SCS-CN) method is widely used in determination of direct surface run-off in long-term (continuous) hydrologic simulation models. Of late, Michel et al. (2005) reviewed the soil moisture accounting (SMA) procedure that lies behind the original SCS-CN method and pointed out severe structural inconsistencies in the treatment of antecedent condition and, in turn, proposed a sounder methodology. However, this method still needs refinement in the definition of initial moisture level (V 0 ) to make it usable in field. Thus, in the present study, the Michel et al. (2005) model is modified to avoid the unrealistic sudden jump in V 0 by incorporating conceptual SMA procedure and variation of daily CN based on antecedent moisture amount instead of antecedent moisture condition. When applied to 17 watersheds from different agro-climatic regions of India, the proposed model simulates daily stream flows better than those due to Michel et al. model. The proposed model performed better in high run-off producing (wet) watersheds than in low run-off producing (dry) watersheds, and the base flow was more and less significant in high and low run-off producing watersheds, respectively, whereas the evapotranspiration showed a reverse trend.

A CN-Based Ensembled Hydrological Model for Enhanced Watershed Runoff Prediction

“…This assessment was accomplished once the pre-storm soil moisture was adjusted in I a based on the recommendation from [11] and was subsequently adopted by other researchers in their studies (e.g., [4,5,12]). In our analysis, we kept the CN as a major parameter obtained from watershed characteristics under normal conditions fixed for all models.…”

“…Different values of V o are found for different AMCs [11] which are differentiated based on P 5 [14]. Using the available CN adjustment formulae from normal (AMC-II) to dry (AMC-I) and wet (AMC-III) conditions, the expression for V o becomes [4]:…”

“…Some researchers (e.g., [26,28]) have specifically mentioned that the cumulative rainfall in the previous five days is not a good proxy of the wetness conditions of the catchment before a flood event. Similarly, the use of a fixed I a in the traditional CN model causes unusual sudden jumps in runoff estimation [1,4,11,12]. To circumvent this issue, we present a continuous spatio-temporal expression for the initial abstraction by replacing the S value in the proposed model with a new expression; SˆˆP P`P 5˙.…”

“…The unavailability of any other simple contender has allowed this model to enjoy a long application history [3]. The widespread application of the CN model has led to its inclusion in hydrological software for surface runoff computations, such as CREAMS, CELTHYM, EPIC, HELP, L-THIA, PRZM, SWAT, SWIM [4], AGNPS, EPA-SWMM, GLEAMS, HEC-HMS, NLEAP, WinTR20, and WinTR55 [5]. Furthermore, the absence of hydrologic gauging stations and the high cost of gauging station installations lead hydrologists to estimate the surface direct runoff for ungauged watersheds using various techniques, and the CN model plays the leading role in such a situation [6].…”

Spatially distributed long‐term hydrologic simulation using a continuous SCS CN method‐based hybrid hydrologic model

“…Several recent studies also consider the SMA procedure in the SCS CN method including Durbude, Jain, and Mishra () and Jain, Durbude, and Mishra () who created and applied a long‐term hydrologic simulation advanced soil moisture accounting model, and Rajib and Merwade () who modified the existing SCS CN module in Soil and Water Assessment Tool. These are implemented based on Michel, Vazken, and Perrin's () concept of the SCS CN formula that needs to define other subformulas for incorporating an intrinsic parameter, S a , and initial soil moisture store level, V 0 .…”